REVIEW OF BACK CONTACT SILICON SOLAR CELLS FOR LOW COST APPLICATION

David D. Smith, James M. GeeSandia National Laboratories

Albuquerque, New Mexico, USA

ABSTRACT. This paper will review back-contact silicon solar cell technologies for low-cost applications. Back contactsolar cells have the advantages of zero or reduced grid shading and simplified module assembly. As silicon material costsdecrease, module assembly will become a significant aspect of overall module costs. There are three design categories ofback contact cells, the Interdigitated Back-Contact (IBC) solar cell, the Emitter Wrap-Through (EWT) solar cell, and thecontact wrap-through solar cell. Each cell design is currently under investigation for low-cost application. The recentdevelopment of a 15.3 % efficient, 41 cm2 EWT solar cell with screen-printed contacts is discussed. High-throughput and low- .. ~cost processing are the current research issues in each cell design.Keywords: Emitter Wrap-Through -1: Interdigitated Back Contact – 2: Screen-printing -3

1. MOTIVATION

Back contact solar cells hold significant promise forincreased performance in photovoltaics for the near fiture.The two major advantages that these cells possess are alack of grid shading loss and co-planar interconnection.Front contacted cells can have up to 10 % shading losswhen using screen printed metrd grids. A front contactcell must also use solder connections that run from thefront of one cell to the back of the next for seriesinterconnection. This procedure is more difficult toautomate than when using co-planar contacts.

The challenge is to produce a high efficiency cell atlow cost using high throughput techniques. ‘lMs has yetto be achieved with a back contact cell design. The focusof this paper will be to review the relevant features ofback contact cells and progress made toward the goal of alow cost version of this device.

All of the back contact cells developed to date fallinto three categories, which can be referred to as theInterdigitated Back Contact (IBC) cell, the Emitter Wrap-Through (EWT) cell and the contact wrap-through cell.IBC includes all of those cell designs with back contactsthat rely upon carrier collection at a rear surface alone.The EWT class of cells can accomplish carrier collectionat both sides and relies upon current conduction from thefront to the back through some sort of perforation in thecell. The contact wrap-through cell maintains a frontcontact grid and brings the busbar or i~ equivalent to theback side through a minimum number of perforations.

2. IBC CELL

The IBC cell must be fabricated on material with along minority carrier diffusion length. The distance fromany point in the cell to the junction must be much lessthan the diffusion length. Excellent front surfacepassivation is required as well.

The IBC cell has the advantage of allowing the rearjunction to be optimized for electrical performance,namely a low Jojunction [1]. There is no need to conductcurrent along a diffused emitter, as is the case with a frontcontact cell. Hence, the tradeoff between series resistanceand @d shading is not present in this design.

The IBC cell has been around since the 1970’s, and isa very well developed technology. SunPower Corp. andAmonix have been commercializing these cells for several

years. The cells are very high efficiency and are marketedfor specifllzed applications. There has been little work inattempting to convert thk device design into a low costcompetitor in today’s one sun flat plate market.

In the classical IBC cell, there are severalphotolithography steps for defining the emitter, backsurface field, contact cuts, and metal gridlines. Onesimplified approach to IBC cell fabrication has beendeveloped by Sinton[l], referred to as the trench mesadesign. Thk process has demonstrated very high cellefficiencies (-22 % for moderate areas of 10.5 cm2). Thkprocess uses one photolithography step to create steps andinterdigitated P+ and N+ diffusions at the back. A fullarea metal deposition on the back side gives a naturalisolation of p and n contacts due to absence of stepcoverageby the deposited metal. This process is veryattractive since it requires no alignments at all, however itis dependent on the properties of a vacuum depositedmetal. Vacuum deposition is generally not viewed as alow-cost process. Also, contact coverage is not selective,and contacts are a major recombination source.

It is possible to combine emitter formation andcontacting into one step by the use of self-dopingmetallizations. This idea has been proposed previously byMeier [2]. The self-doping metal concept uses ametaVdopant compound applied to the silicon. This isfollowed by a high temperature step above the metal-silicon eutectic temperature to form an epitaxial siliconjunction or back surface field by liquid phase ~owth. Themetal remains to form a contact to the grown layer. ‘lWsconcept has the advantage of reducing process steps andproducing a contact that is self-aligned to the junction.The process would require two applications of differentself-doping metal compounds and one high temperaturecycle. The second metal would need to be aligned to thefirst metal gridline pattern. A 10.4 % efficient cell wasreported using aluminum as the p-contact and rmtimony-doped silver as the n-contact [2].

One drawback to the self-doping metal approach isthat the junction area, and hence, metal coveragefractions, are high on the back surface. This adverselyaffects light trapping by reducing back surface reflectivity.Additionally, contact recombination is higher whencompared to a selective contact. However, it is importantto note that minimizing contact recombination requires athick emitter of moderately high doping under the contact.In conventional emitter formation techniques, this requires

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DISCLAIMER

This report was prepared as an account of work sponsoredbyan agency of the United States Government. Neitherthe United States Government nor any agency thereof, norany of their employees, make any warranty, express orimplied, or assumes any legal liability or responsibility forthe accuracy, completeness, or usefulness of anyinformation, apparatus, product, or process disclosed, orrepresents that its use would not infringe privately ownedrights. Reference herein to any specific commercialproduct, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constituteor imply its endorsement, recommendation, or favoring bythe United States Government or any agency thereof. Theviews and opinions of authors expressed herein do notnecessarily state or reflect those of the United StatesGovernment or any agency thereof.

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DISCLAIMER

Portions of this document may be illegiblein electronic image products. Images areproduced from the best available originaldocument.

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Structural Chemistry Page 2

measure of ruffling it is the only structural parameter that does not overestimate the extent of

ruffling due to the presence of saddling. The average distance between the C~ carbons and the

plane comprising the four nitrogens, the four meso carbons and the cobalt ion is the best

structural measure of saddling. No structural parameters were found that could be used in

principal component analysis to find PC’s that quantified the non-planar deformations in

cobalt(III) porphyrins. The cluster analysis was able to separate the sad, ruf and planar

structures, however the preparation and symmetry adaptation of all the structures was

complicated and was no more informative than the use of some of the univarient structural

parameters. The NSD deformations are related to the vibrational energies and motions of the

macrocycle and are thus the preferred description, but the more easily obtained

parameters are useful measures of the normal coordinate deformations whenever a

analysis is not possible.

structural

full NSD

..

I

Structural Chemistry Page 3

Introduction

Porphyrins are conjugated hetero-macrocyclic molecules consisting of four pyrrole rings

joined by bridging carbons, Figure 1. They are excellent ligands, usually tetradentate, for a wide

variety of metal ions. In such complexes, the porphyrin acts as a dianion. Because of their

importance in biology and chemistry, porphyrins have been widely studied [1].

At one time it was thought that the aromatic porphyrin macrocycle would be planar. In

fact early structure determinations constrained the macrocycle to be planar. However when high

quality crystallographic determinations of porphyrins and metalloporphyrins began to appear, it

was soon obvious that the porphyrin ring was subject to a number of distortions and was often

distinctly non-planar. The non-planarity of porphyrins is biologically relevant [2] and influences

the chemical properties of porphyrin complexes [3].

Most deformations of the porphyrin core are in a direction perpendicular to the tetra-aza

plane. However, deformations can occur even when the macrocycle is planar. Such in-plane

deformations are less common, and are reflected in such parameters as the CU-Cmeso-Cu and

Ca-N-Cu angles. Classic examples are SnOEPC12 and SnTPPC12 (OEP = 2,3,7,8,12,13,17,18-

octaethylporphyrin, TPP = 5,10, 15,20-tetraphenylporphryin) [4,5]. The macrocycle is planar

even though the Sri-N distances are fairly long, causing expansion of the porphyrin core. The

four pyrrole rings are planar in all conformations.

Most non-planar deformations can be classified into six classes, Figure 2. They are based

on simple symmetric deformations, one of each out-of-plane symmetry classification of the (D,,)

point group of the square-planar macrocycle. More complicated asymmetric distortions that are

--- . -- -s..?.. . . -- ., -.-->,. -. --:------ ., ---------- - ,. -. . . . . . . ,WL,*17”.”,,=---., >, ; -..Z ! ;.TT,--- ;Z..-, ,

I

Structural Chemistry Page 4

composed of combinations of these simple distortions are also found. In the ruffled type of

deformation (ruj), the meso carbons are alternatively above and below the porphyrin mean plane.

The Ca-N-N-Ca torsion angle involving pyrrole rings on opposite sides of the macrocycle,

Figure 1, is a measure of ruffling that can range from 0° to as much as 600. Factors that can lead

to this type of deformation are short M-N bond distances (e.g. the Ni-N distance of 1.92 ~ in the

ruffled form of NiOEP) and peripheral substitution [2,6].

In the saddle type of deformation (sad), the meso-carbons are in the mean plane of the

porphyrin, and one opposing pair of pyrrole rings tilts up while the other pair tilts down (Figure

2). The Ca-N-N-C& torsion angle is OO. Highly substituted porphyrins can lead to such

conformations (e.g. CU(II) octaethyltetrapheny lporphyrin) [6]. This type of deformation is also

typical of m–-cationradical complexes. In the wave type of deformation (wav) (Figure 2), two

opposing pyrrole rings are tilted up and down with respect to the porphyrin mean plane. This

energetic type of deformation is less common than the previous two. Often the wav deviations

from planarity are minor, though examples where these deviations are large are known. In the

dome type of deformation (dcvn), all of the P carbons are on one side of the porphyrin mean

plane, the meso carbons are in (or near) the plane and the u carbons and the nitrogens are above

the plane. Typically this type of deformation occurs when the macrocycle is coordinated to a

large metal atom. Doming is also usually small because of the large energy required for

deformation along the dom normal coordinate [7]. The degree of doming has also been shown to

depend on the nature of the axial Iigand [8].

In order to describe and analyze porphyrin distortions, a simple method of qualifying and

quantifying the distortions is needed. Ideally this method can then be used in conjunction with

other computational calculations to establish the reasons why specific non-planar deformations

*

Structural Chemistiy Page 5

are adopted, and what the chemical consequences of the non-planar deformations are.

A normal-coordinate structural decomposition (NSD) procedure has been used to

characterize and quantify porphyrin deformations in proteins [7,2]. The method determines the

out-of-plane distortions in terms of the equivalent distortions along the lowest-frequency normal

coordinates of the porphyrin [9]. Prior NSD analyses of porphyrins have been mostly limited to

protein structures from the protein databank (pdb). Remarkably, this work has revealed

previously hidden conservation of the non-planar conformation of porphyrin for many protein

types. For example, c-type cytochromes with their covalently bound heroes show a characteristic

distortion that is predominately ru~ and peroxidases exhibit a predominately sad distortion. The

conservation of these characteristic macrocycle structures for proteins, which differ in their

amino acid sequences but have the same function, indicates a functional role for the distortion.

The success of this approach in analyzing hemeprotein structures suggests a similar approach for

crystal structures of synthetic porphyrins might be informative.

The latest version of the Cambridge Structural Database (CSD), version 5.19, has

214,000 X-ray and neutron diffraction structures of organocarbon compounds. Many of the

structures in the CSD have a common backbone, e.g. there are 1,692 structures with porphyrin

core (see Table 1). Analyses of such congeneric families are very useful as they reveal the

different conformations the backbone structure can adopt in the different environments found in

the crystals. This can provide information about the conformations available to the backbone,

how the conformers can interconvert, and the environmental factors that are responsible for

certain conformations [10]. Furthermore, if one assumes that the porphyrin backbone will adopt a

low energy conformation in most crystal structures, then the confirmational space spanned by

the crystal conformations in the CSD can be equated and compared (qualitatively, not

quantitatively) with the potential energy surface of the porphyrin itself. In this study, therefore,

Structural Chemist~ Page 6

we have used the Co porphyrin structures in the CSD for this purpose.

Our cluster analysis of cobalt(lII) [11], copper(n) [12] and nickel(II) [13] complexes

containing the 14-membered tetra-aza macrocycles found that the macrocyclic ring structures

were effectively separated according to their conformation by an agglomerative, hierarchical,

single-link clustering method. Some reservations have been expressed that single-link methods

can link dissimilar clusters that contain bridging outlying members. However, since this was not

found to be a problem in the clustering of transition metal fourteen- or six-membered rings

[14,15,16,17], we attempted to use cluster analysis to separate the cobalt(III) porphyrins in the

CSD based on their non-planar deformations using cluster analysis.

In this paper we also describe the utility of principle component analysis to differentiate

between different non-planar deformations of cobalt(III) porphyrins, and compare these results

with normal-coordinate structural decomposition analysis. Raithby and co-workers have

published three articles in which they have undertaken a systematic cluster and principal

component confirmational analyses of metal and metal-free 12-, 14-, 15- and 16-membered oxa

and this macrocyclic ligands, and their derivatives [18,19,20]. While principal component

analysis of the 12-, 14- and 16-membered macrocycles was able to represent the different

conformations in torsional space, the conformations adopted by the 15-membered rings were not

well by represented by PCA.

Experimental

A search of the Cambridge Structure Database (CSD)[21 ] v5. 19 was performed to find all

the cobalt(lII) porphyrin complexes. They are listed in Table 2. The Cartesian coordinates and

structural parameters for these compounds were saved and symmetry expanded.

Structural Chemistry Page 7

Normal Coordinate Analysis: All the structures were analyzed by normal-coordinate

stmctural decomposition

represented in Figure 2.

Cluster Analysis:

(NSD) as described in the literature [7,2,9] and as schematically

All the substituents, including hydrogens, were removed from the

porphyrin backbone of all the complexes listed in Table 2. The atoms of every structure were

renumbered such that the corresponding atoms of each ring were given the same number.

Proximity matrices were obtained by determining the pairwise distances between rings using the

root mean squared deviation (rms) differences between corresponding external dihedral angles

and the rms displacement between pairs of identically numbered atoms after optimal rigid-body

superimposition. Cluster analysis was performed using the xcluster program [22].

Principal Component Analysis: The symmetry expanded Cartesian coordinates were

imported into VISTA for principal component analysis.

Results and Discussion

Normal-Coordinate Structural Decomposition: The normal-coordinate structural

decomposition (NSD) procedure has been used to characterize and quantify porphyrin

deformations in protein structures [7,23] and. in a few porphyrin crystal structures [24]. The

method determines the out-of-plane distortions in terms of the equivalent distortions along the

lowest-coordinates of the macrocycle [24], and has been used to determine the out-of-plane

displacements (~) along the lowest-frequency normal coordinates for more than 1300 iron

porphyrins in the PDB [25]. Table 3 lists the NSD results for the non-planar deformations of all

the cobalt(IH) porphyrins examined.

Structural Chemistry Page 8

Structural Parameters: Numerous other structural parameters have been used to quantify

non-planar deformations. In order to establish their utility we have compared them with the out-

of-plane displacements (~) along the ruf and sad coordinates given in Table 3. The Ca-N-N-Cu

torsion angle has been used a quantitative measure of ruffling [26]. In order to determine

whether the Ca-N-N-Cu dihedral can quantify the amount of ruffling present in the porphyrins

listed in Table 2 we compared the Cu-N-N-Ca dihedral angle to the symmetric B,Unormal

coordinate deformation (a direct measure of ruffling). Figure 3 is a plot of the ruf deformations

versus the average absolute value of all the trans Ca-N-N-Ca dihedral angles for all the cobalt(III)

porphyrins examined. The plot has a correlation coefficient of 0.941. It is apparent from the

figure that the trans Ca-N-N-Ca dihedral angle overestimates the amount of ruffling in the

wadric, zawfei, acporc and kuzzuo structures. Wadric is the most sad distorted porphyrin in this

study and the large out of plane deformations of the pyrrole rings in wadric lead to an incorrect

prediction of the amount of ruffling. Zawfei, acporc and kuzzuo are the next most saddled

complexes. If the structures of wadric, zawfei, acporc and kuzzuo are removed the correlation

coefficient increases to 0.998.

Other effective measures of ruffling are the C~aO-Co-C~uOangle[27] (r = 0.969), and the

average distance of the C~~Oatoms to the plane of all non-hydrogens in the complex (r= 0.979).

In both cases the substantial saddling found in wadric led to an overestimation of its ruffling.

Jentzen et al. [8] have used the average N-Ct-N angle, where Ct represents the center of

the porphyrin macrocycle and N the opposite nitrogens, as a measure of the saddling

deformation. We have not been able to find any other literature references to structural

parameters that have been used to quantify saddling deformations. In order to establish whether

there are structural parameters that are better at quantifying ruffling and saddling than those

Structural Chemistry Page 9

discussed above, we have examined all the structural parameters given in Table 4. The best

measures of saddling were

four nitrogens and cobalt,

the average distance of the Cp carbons to the plane comprising the

and the average distance between the C~ carbons and the plane

comprising the four nitrogens, the four meso

parameter that best quantifies ruffling is the cis

carbons, and the cobalt ion. The structural

Ca-N-N-Ca dihedral angle (r= 0.986 for all

complexes). It is also the only parameter that does not overestimate the extent of ruffling due to

the presence of saddling.

The structural parameters described in this section used a single descriptor, such as an

average torsion angle, to quantify the non-planar deformations. In the next two sections we

describe the use of multivarient methods.

Principal Component Analysis (PCA)

The goal of PCA is to generate linear combinations of principle components that describe

the greatest variance over all the data. Ideally a small number (C) of principal components will

describe a large proportion of the total variance. The principle components, (PC)j, can be

expressed as linear combinations of the original data [xi(i=l ,2,3 .. .p)] where p is the number of

dimensions of the original data as follows

(Pc)j = aljxl + Zizjxz + . . . . . . . . . ZipjXp

The coefficients ~j indicate the contribution of each variable xi to the PCj. Coefficients of zero or

close to zero indicate that their associated xi’s do not significantly contribute to the PC, while

coefficients that are significantly higher than the others are closely aligned to the PCj. One of the

difficulties in using PCA is that there is no clear relation between the PC and the structural

Structural Chemistry Page 10

parameters used in the analysis and it is not always possible to interpret the PC’s in chemical

terms.

Table 5 lists the structural parameters used in some of the more successful principal

component analyses. None of the PCA were able to quantify the degree of ruffling and/or.

saddling as well as the structural parameters described in the previous section. PCA were

performed using only distances, angles or torsions, and using combinations thereof. Surprisingly

the best results were obtained when the PCA were based on a combination of two- and three-

body interactions.

Cluster Analysis

In cluster analysis, one attempts to group all the elements of interest into separate clusters

in such a way that all the elements within a cluster are very similar to each other and dissimilar to

elements in other clusters [28, 29]. Cluster analysis can be used to group any elements with

quantifiable properties. In order to perform a cluster analysis, one has to have a measure of

difference between elements, a method of separating the items of interest, and some statistical

measure for determining the clustering level which is the most significant.

In all clustering methods, the first step is to set up a distance matrix that gives the

distance from each element to every other element. Typical interconformational distance

measures are the root mean squared (rms) displacements of equivalent atoms in different

molecules, which are taken after all the molecules have been optimally superimposed, and the

rms differences of dihedral angles.

The distance matrix is then used to cluster the data. We will only describe the

agglomerative hierarchical single link method, as this is the technique we intend to use. All

conformations are initially taken as separate clusters. This is known as clustering level 1 and

Structural Chemist~ ‘ Page 11

there are as many clusters as there are elements. At clustering level 2, the two conformations that

are the closest to one another are joined to form a new cluster with two members. If N points are

being clustered, there are N-1 clusters at clustering level 2. This process is continued until at

cluster level N all the points will have been joined into one large cluster with N members. This

technique is hierarchical because it starts with all the conformations in separate clusters and ends

up with all the conformations in a single cluster. It is agglomerative because if two clusters

contain the conformations that are next closest to each other, they are fused into a larger cluster,

and it is a single link method because two clusters are joined on the basis of the two closest

conformations within the two clusters being joined (see Figure 4). A common problem with

single link methods is that two clusters that are dissimilar can be joined into one larger cluster by

outlying points in each cluster. However, we have found that this is not a large problem in small

inorganic systems.

The most effective cluster analyses were those obtained after comparing all the external

atoms or dihedral angles, that is, those involving the 8 ~-carbons, 8 et-carbons and 4 meso-

carbons. In order to find all the symmetry related conformations of these 20-membered ring

systems, they were rotated 20-fold. They were ordered and clustered according to the rms

displacement between identically numbered atomic pairs after rigid body superimposition, and

the rms differences between the external torsion angles. Figure 3 shows the clustering mosaic

obtained by using the rms deviation of the atomic positions after atomic superimposition as a

distance measure, similar results were obtained by comparing the external dihedrals.

The distance maps and clustering mosaics were used to determine that the best clustering

level was level 41. Figure 4 shows the 9 clusters at level 41 and Table 3 lists the cluster members

and their sad (Bzu)and ruf (B,U)deformations as determined by NSD analysis. The structures in

cluster 1 are all saddled, those in cluster 2 are planar and those in cluster 3 are ruffled, see Figure

Structural Chemistry Page 12

5 and Table 3.

A cluster analysis superimposing the four C~wO,eight Ca and four nitrogen atoms with a

16 fold symmetry, and clustering them according to their torsional or atomic overlaps was also

able to separate the porphyrin complexes into saddled, ruffled and planar complexes.

Conclusion

The cis Ca-N-N-Ca dihedral angle is the best structural measure of ruffling. Many of the

other structural measures described in this paper and discussed in the literature overestimate the

amount of ruffling in structures that are saddled as well as ruffled. The cis Ca-N-N-Ca dihedral

angle is the only structural parameter that does not overestimate the extent of ruffling due to the

presence of saddling. The average distance between the Cp carbons and the plane comprising the

four nitrogens, the four meso carbons and the cobalt ion is the best univariate structural measure

of saddling.

We were not able to find any structural parameters that could be used in PCA to find

PC’s that quantified the non-planar deformations in cobalt(III) porphyrins. The cluster analysis

was able to separate the sad, ruf and planar structures, however the preparation and symmetry

adaptation of all the structures was involved and was no more informative than the use of some

of the univarient structural parameters listed in Table 4.

One of the advantages of the NSD technique is that it is able to quantify all six non-planar

deformations shown in Figure 2. Furthermore, the NSD deformations are related to the

vibrational energies and motions of the macrocycle and are thus the preferred description, but as

we have shown other more easily obtained structural parameters are useful measures of the

normal coordinate deformations whenever a full NSD analysis is not possible. The cobalt(III)

Structural Chemistry Page 13

porphyrins discussed in this paper do not undergo large wav, dom and pro deformations and they

were not considered in our analysis.

Acknowledgements

MZ is a Henry Dreyfus Teacher-Scholar. LVD acknowledges a Keck undergraduate

summer fellowship. Sandia is a multiprogram laboratory operated by Sandia Corporation, a

Lockheed Martin Company, for the United States Department of Energy under Contract DE-

AC04-94AL85000.

Structural Chemistry Page 14

Table 1: Number of structures in the Cambridge Structural Database

Metal Ion (congeneric family) Number of Structures

Transition Metal (Porphyrin) 1,318

Fe (Porphyrin) 407

Co(Porphyrin) 110

Ni(Porphyrin) 102

Cu(Pomhvrin) 79

Structural Chemistq

Table 2: CSD Structures examined.

REFCODES

Acporc[30] Nocwil[31 ]

Cosjup[32] Ntpolc[33]

Cotwen[34] Nuwpok[35]

Ctpoco[36] Oepcoi 10[37]

Cuppei[38] 0epcop[39]

Dmipco[401 Paclio[411.-

Fag;iz[42] - - “ Pibnuj[43]

,Folwim(441 Pozaier451A-.

Fulbap[~6]- Pozqok[47]

Gamtap[48] Ptporc[49]

Gepgaj [50] Pucpae[51 ]3iztis[52] Reqqej [53]

3ambay[54] Roqbee[55]

+Iecziy[56] Sirroa[57]

Heqzei[58] Sirrug[59]

Heqzim[60] Tefpez[61 ]

Imptco[62] Tefpid(631I ---

lKebmin(641 hborco10[6514 . .

Kuzzio[66]- Tporcp[67]

KUZZOU[68] Tporcpl 1[69]

Libbut[70] Wadric [71]

Libcaa[72] Zawfei[73]

Libcee[74] Zonqoi[75]

Mptpco[76]

Mxpoco[77]Neycav[78]

NeycavOl [79]

Page 15

Structural Chemistry Page 16

Table3: Cluster membership atclustering level 41forthe cluster analysis ofdlthe complexes

in Table 2.They were separated on the basis of therms deviation of the pairwise difference of

corresponding atoms after superimposition of the 8 ~-carbons, 8 a-carbons and 4 meso-carbons.

resulting cluster mosaic is shown in Figure 3. The out-of-plane deformations (~) were determin[

NSD.

1 ACPORC-O 0.009 0.0KUZZIO-O 0.181 0.0.. , “.”7

I KUZZ

h--l-%%FAGCIZ-1HAMBAY-O 0.071 _____ ----- , ----- 1HEQZEI 0.063 0.000 0.000 IO. 124 IiSIRROA-O 0.008 0.000CUPPEI o.16nTEFPID 0.1:SIRRUG 0.0/HECZI rNEYCAV-O

HEI NEYCAVO1

Cluster I Ref. Code wav (x) pro dom wav (y) sad ruf# (U) (A,,,) (A,,,) (EOv) (B2,,) (B,,,)

)18 0.014 0.010 1.476 0.219)11 n nA’2 0.155 1.121 0.465

Ou-o 0.188 0.058 0.000 0.152 1.410 0.173101-0 0.092 0.031 0.121 0.014 0.695 0.345EN-O 0.032 0.067 0.107 0.016 0.069 0.029mm 0.000 0.082 0.174 0.000 0.000 0.000

0.162 0.000 0.000 0.233 0.000 0.000_—0.006 0.(-)57 0(-)1rl 0.016 0.023

).000 0.0000.000 0.131 0.000 0.000

0.000 0.000 0.101 0.000 0.000;6 0.000 0.000 0.132 0.000 0.00086 0.000 0.000 0.081 0.000 0.000

r-r 0.182 0.000 0.000 0.037 0.000 0.0000.136 0.011 0.000 0.004 0.096 0.0280.020 0.008 0.022 0.035 0.037 0.003

Jr 0.10 0.000 0.000 0.044 0.000 0.000.- .

0.051 0.000 0.000 0.138 0.000 0.0000.136 0.012 0.003 0.003 0.097 0.033

I 0.037 0.000 0.000 0.037 0.000 0.000,.-—0.000 0.026 0.064 0.060 0.135

co 0.089 0.002 0.109 0.016 0.049 0.123:010 0.171 0.000 0.000 0.048 0.000 0.000!4P 0.026 0.008 0.053 0.015 0.230 0.050:0-0 0.022 0.007 0.048 0.093 0.136 0.168.

0.099 0.015 0.010 0.049 0.192 0.2470.118 0.007 0.135 0.000 0.284 0.260---

0.018 0.070 0.115 0.280 0.045-. 0.067 0.000 0.000 0.046 0.000 0.000

0.038 0.003 0.147 0.040 0.131 0.0320.139 0.039 0.142 0.108 0.183 0.0730.027 0.008 0.012 0.004 0.314 0.5990.084 0.026 0.079 0.063 0.190 0.4010.027 0.000 0.004 0.041 0.861 0.476-—

0.018 0.114 0.035J 0.445 0.428

H%W’’UU74I TPOR[

Hx_l=+%&’0082

I OEPCOI1O

H=RO BEE-OPACLIO-OPIBNUJ-OCOSJUPFOLWIM I 0.026

listed

The

:d by

Structural Chemistry Page 17

3 MXPOCO 0.005 0.034 0.013 0.042 0.259 1.054NOCWIL-O 0.196 0.030 0.107 0.152 0.215 0.279TPORCP-O 0.000 0.000 0.000 0.000 0.189 1.181NTPOLC-O 0.000 0.000 0.000 0.000 0.006 1.685POZQIE-O 0.025 0.000 0.031 0.049 0.062 1.760PUCPAE 0.126 0.010 0.034 0.045 0.181 1.761POZQOK-O 0.102 0.000 0.030 0.099 0.280 1.571TPORCP11 0.000 0.000 0.000 0.000 0.171 1.202

4 KEBMIN 0.103 0.041 0.057 0.056 0.774 0.9835 GEPGAJ-O 0.009 0.043 0.136 0.004 1.208 1.2746 GAMTAP-O 0.032 0.011 0.084 0.042 0.737 1.3527 TEFPEZ-O 0.025 0.014 0.060 0.117 0.603 0.9828 WADRIC-O 0.019 0.011 0.003 0.038 3.575 0.1489 ZAWFEI-O 0.040 0.000 0.009 0.028 2.767 0.808

Structural Chemistry Page 18

Table 4: Univarient structural parameters examined in the structural analysis of all cobalt(III)

porphyrin complexes.

Average Structural Parameters Correlation coefficient for structuralparameters vs. out-of-planedeformations

Saddled (B,,,)0.406

Ruffled (B,tj0.941/Trans Ca-N-N-Ca torsion/

/Cis C~-N-N-C~ torsion/Cm,<fi-Co-Cme<nangleAngles between opposing pyrrole planesAngles between all pyrrole planesDistances between centroids of opposing

W’rrolesDistances between the opposing C~’sDistances of C~’s to plane of all 4 N andco.

0.200

0.095

0.9860.969

0.6640.139

0.8120.237

0.814 0.411

0.139 0.2370.965 0.253

Distances of Cp’s to plane of 4 N, C~fiOandco

0.969 0.268

Distances of Ca’s to plane of 4N, C~uO,andco

0.657 0.804

Distance of Co to plane of all atoms except 0.000 0.226

Distances of Cm,,n’sto plane of all atomsDistance of C~~O’s to plane of all 4N and

0.0890.089

0.9790.990

Distance of nitrogen’s to plane of all atoms 0.828 0.063

Structural Chemistry Page 19

Table 5: Structural parameters used in principal component analyses that were best able to quantify sad

and ru~distortions.

Structural Parameters Correlation with NSD % variance

Cis C.-N-N-Ca PC1(O.808) ruffled PC1= 84.61%Opposing C .n-Co-Cme,oCis C.-N-N-C. PC1 (0.691) ruffled PC1= 73.62%All Cmp<n-Co-Cme<oCis C.-N-N-C. PC1 (0.528) ruffled PC1= 77.32%Opposing C~MO-Co-Cm= PC2 (0.496) saddled PC2= 14.84%Angles between best plane ofeach pyrroleDistance between Cp’s PC1 (0.620) saddled values PC1= 95.78%Distance between oppositecentroids of the pyrrolesDistance between opposite PC1 (O.176) ruffled PC1= 65.87%centroids of the pyrroles PC2 (0.460) saddled PC2= 30.48%Opposing Cme<m-Co-Cme<nAngles between the opposite PC1 (0.591) saddled PC1= 85.22%plane of pyrrolesDistance between Cband CDDistance of Cp and C~aOto PC1 (0.719) saddled PC1= 60.73%plane of all 4N and Co PC2 (0.585) ruffled PC2= 29.32%Cis C.-N-N-C. PC1 (0.467) ruffled PC1= 51.78%Opposing C~=O-Co-C~uO PC2 (0.727) saddled PC2= 33.91%Distance of Cp and C~aOtoplane of all 4N and CoDistance of Cp to plane of all 4 PC1 (0.768) saddled Pcl= 86.81%N and CoDistance of C~uOto plane of all PC1 (0.678) ruffled PC1= 94.65%4 N and Co

..--, .

.

Structural Chemistry Page 20

Figure 1: Porphyrin macrocycle and nomenclature used. A cis Cp-N-N-CP dihedral angle is shown in

bold.

Structural Chemistry Page 21

\

Tiiz-’-lntf (Blu)

dom (A2u)

*

\ /

/ \

wav(y) (Egy)

L? Ihrc

P

r’ i

-11

-().5 0.0 0.5 1.0

Deformation (in ~)

Figure 2: Illustrations of the lowest-frequency out-of-plane eigenvectors in the coordinate space, for

each of the normal deformations used in describing the non-planar distortions of the porphyrin

macrocycle.

t

Structural Chemistiy

2

zawfei ❑

wadric acporc ~❑ kuzzuo ❑

o I140 150 160 170 180 190

Page 22

Average /trans Ca-N-N-Ca torsion/ (0)

Figure 3: Plot of the average trans Ca-N-N-Ca torsion angle vs. the NSD ruffled out-of-plane (Blu)

deformation (correlation coefficient 0.941).

.

Structural Chemistry

Cluster Level

41 _,

C1uster Number

.

Page 23

[

~lh-11111111111

,,

1 2 3

Figure 4: Clustering mosaic for the cluster analysis of all the complexes listed in Table 2.They were

separated on the basis of therms deviation of the pairwise difference of corresponding atoms after

superimposition of the 8 &carbons, 8 a-carbons and 4 meso-carbons. Clusters 1 ,2 and 3 at clustering

level 41 are shown. The individual members of these clusters are also listed in Table 3 and shown in

figure 5.

.

Structural Chemistry

Cluster 1 Sad

Page 24

Cluster 2 Planar

Figure 5: Overlap of all the members of clusters 1 (A), 2 (B) and 3 (C) of the cluster analysis described

in Table 3 and Figure 4.

Cluster 3 Ruff

,

Structural Chemist~ Page 25

1. The Porphyrin Handbook Kadish, K.M.; Smith, K.M.; Guilard, R. Eds.; Academic Press, 2000.2. Shelnutt, J.A. The Porphyrin Handbook Kadish, K.M.; Smith, K.M.; Guilard, R. Eds.; Academic Press, 2000,vol. 7.3. Parusel, A.B,J.; Wondimagegn, T.; Ghosh, A. J. Am. Chem. Sot. 2000,122,6371.4. Cullen, D.L.; Meyer, E.F. Jr. Acts Crysfallogr., Sect. 1?.1973,29,2507.5. Collins, D,M.; Scheidt, W.R.; Hoard, J.L. J Am. Chem. Sot. 1972,94, 6689.6. Sparks, L.D.; Medforth, C.J.; Park, M. -S. Chamberlain, J.R.; Ondrias, M.R.; Senge, M.O.; Smith, K.M.; Shelnutt,J.A. J. Amer. Chem. Sot. 1993,115,581.7. Shelnutt, J.A.; Song, X.-Z.; Ma, J.-G.; Jia, S.-L.; Jentzen W.; Medforth C.J. Chem. Sot. Rev. 1998,27, 31 andreferences thererin.8. Scheidt, W.R.; Lee Y.J. Structure and Bonding. 1987,64, 1.

9. Jentzen, W.; Song, X.-Z.; Shelnutt, J.A. J. Phys. Chem. B 1997,101, 1684.10. Orpen A,G. J. Chem. Sot. Dalton Trans. 1993,191.11. Cooper, C. F. Jr.; Zimmer, M. Structural Chem. 1999,10, 17.12. Bakaj, M.; Zimmer, M. J. Mol. Struct. 1999,508,59.13. Donnelly M.A.; Zimmer, M. Inorg. Chem. 1999,38, 1650.14 DaCruz, M.F.; Zimmer, M. Znorg. Chem., 1996,35,2872.15 DaCruz M.F.; Zimmer, M. Znorg. Chim. Acts, 1997,261, 181.16 Norenberg, K.M,; Shoemaker, C.M.; Zimmer, M. J. Chem. Sot., Dalton Trans., 1997, 1521.17 DaCruz M.F.; Zimmer, M. Znorg. Chem., 1998,2,366.18 Raithby, P.R; Shields, G.P; Allen, F.H. Acts C~st. 1997, B53, 241.19. Raithby, P.R; Shields, G.P; Allen, F.H. Acts C~st. 1997, B53, 476.20. Allen, F.H; Raithby, P.R; Shields, G.P. Struct. Chem. 1997,8,385.21. Allen, F.H; Kennard, O. Chem. Des. Auto. News, 1993,8,31.22. Shenkin, P.S; McDonald, D.Q. J. Comp. Chem. 1994,15, 899.23. Shelnutt, J.A. The Porphyrin Handbook; Kadish, K.M.; Smith, K.M.; Guilard, R. Eds.; Academic Press, 2000,vol. 7.24. Jentzen, W.; Song, X.-Z.; Shelnutt, J.A. J. Phys. Chem. B 1997, 101, 1684.25. Shelnutt, J.A, The Porphyrin Handbook, Kadish, K.M.; Smith, K.M.; Guilard, R. Eds. 2000, Vol. 7.26, Vangberg, T.; Ghosh, A. J. Am. Chem. Sot. 1999,121, 12154.27. Munro, O.Q.; Bradley, J.C.; Hancock, R.D.; Marques, H.M.; Marsicano, Wade, P.W. J. Am. Chem. Sot. 1992,114,7218.28. Shenkin P.S.; McDonald D.Q. J. Comp. Chem. 1994,15,899.29. Torda A.E.; Van Gunsteren W.F. J. Comp. Chem. 1994,12, 1331.30. Kastner, M.E; Scheidt, W.R. J. Organomet. Chem. 1978, ]57, 109.31. Clement, T.E; Nurco, D.1 Smith, K.M. lnorg. Chem. 1998,37, 1150.32. Doppelt, P; Fischer, J; Weiss. R. J.Am.Chem.Soc.1984, 106,5188.33. Kaduk, J.A; Scheidt, W.R. Inorg. Chem. 1974,13, 1875.34. Masuda, H; Taga, T; Sugimoto, H; Mori, M. J Oraganomet. Chem. 1984,273,385.35. Xiangdong, Jiao ; Jinwang, Huang; Liangnian, Ji ; Xing, Wang. J. Inorg. Chem. (Wuji Hua.xueXuebao). 1997,13, 129-2.36. Sakurai, T; Yamamoto, K; Naito, H; Nakamoto, N. Bull. Chem. Sot. Jpn. 1976,49,3042.37. Little, R.G; Ibers, J.A. J.Am. Chem. Sot. 1974,96,4452.38. Doppelt, P; Fischer, J; Weiss, R. Inorg. Chem. 1984,23,2958.39. Little, R.G; Ibers, J.A. J,Am. Chem.Soc. 1974,96,4440.40. Dwyer, P.N Madura, P; Scheidt, W.R. J.Am.Chem.Soc.1974, 96,4815.

,“ . ,- .- .7-< Y,--- -“ .-:-- , : “f--- ~-------- -- .. ---., . ..-. —.

. .

Structural Chemistry Page 26

41. Bang, H, Edwards, J.O; Kim, J; Lawler, R.G; Reynolds, K, Ryan, W.L Sweigart, D.A. J.Am. Chem, Sot. 1992,114,2843.42. Ciurli, S; Gambarotta, S, Floriani, C; Chiesi-Villa, A; Guastini, C. Angew. Chem. ht. Ed. Engl. 1986,25,553.43. Balch, A.L; Mazzanti, M; Olmstead, M.M. Inorg. Chem. 1993,32,4737.44. Doppelt, P; Fischer, J; Ricard, L; Weiss, R. New J. Chem. (Nouv. J. Chim.) 1987,11,35745. Simonato, J.-P; Pecaut, 1 Marchon, J.-C. J.Am. Chem. Sot. 1998,120,7363.46. Arasasingham, R,D; Balch, A.L; Olmstead, M.M; Renner, M.W. lnorg. Chem. 1987,26,3562.47. Simonato, J.-P; Pecaut, L Marchon, J.-C. J.Am. Chem. Sot. 1998,120,7363.

“ 48. Timura, Y; Sakurai, Z Yamamoto, K. Bull. Chem. Sot. Jpn. 1988,61,821.49. Scheidt, W.R. J.Am. Chem. Sot. 1974,96,84.50. Sparapany, J. W, Crossley, M. L Baldwin, J.E, Ibers, J.A. J.Am. Chem. Sot. 1988,110,4559.51. Toronto, D; Sarrazin, F; Pecaut, J; Marchon, J.-C; Shang, M; Scheidt, W.R. lnorg. Chem. 1998,37,526.52. Yang Cao, J.L.Petersen, A.M.Stolzenberg. ltzorg.Chem.1998, 37,5173.53. Cesario, M; Giannotti, C; Guilhem, J; Silver, L Zakrzewski, J. J.Chem.Sot, Dalton Trans. 1997,47.54. Byrn, M.P; Curtis, C.Z Hsiou, Yu; Khan, S.1; Sawin, P.A; Tendick, S.K Terzis, A; Strouse, C.E. J. Am. Chem.SOC. 1993,115,9480,55. Cao, Yang; Petersen, J.L; Stolzenberg, A.M. hzorg. Chem. Acts. 1997,263, 139.56. Scheidt, W.R, Turowska-Tyrk, I. Inorg. Chem. 1994,33, 1314.57. Kadish, K.M; Araullo-McAdarns, C; Han, B.C; Franzen, M.M. J.Am. Chem. Sot. 1990,112,8364.58. Smirnov, V.V; Weller, E.K, DiMagno, S.G. Inorg. Chem. 1998,37,4971.59, Kadish, K.M; Araullo-McAdams, C; Han, B.C; Frazen, M.M; J.Am.Chem.Soc. 1990,112,8364.60. Smirnov, V.V; Weller, E.K, DiMagno, S.G. Inorg. Chem. 1998,37,4971.61. Goldberg, I; Krupitsky, H; Stein, Z; Hsiou, Yu; Strouse, C.E. Supramolecular Chemiwy. 1994,4,203.62. Scheidt, W.R. J.Am. Chem. Sot. 1974,96,90.63. Goldberg, L Krupitsky, H, Stein, Z Hsiou, Yu; Strouse, C.E. Supramolecular Chemiwy. 1994,4,203.64. Milkolaiski, W; Baum, G; Massa, W; Hoffman, R.W. J. Organomet. Chem. 1989,376,397.65. Lauber, J.W, Ibers, J.A J.Am. Chem.Soc. 1994,96,4447.66. Guilard, R Lopez, M.A; Tabard, A; Richard, P; Lecomte, C; Brandes, S; Hutchison, J.E; Collman, J.P. J. Am.Chem. Sot. 1992,114,9877.67. Madura, P; Scheidt, W.R. Inorg. Chem. 1976,15,3182.68. Collman, J.P; Hutchison, J.E; Lopez, M.A; Tabard, A; Guilard, R; Seek, Won. K; Ibers, J.A; Her, M.L. J.Am. Chem, Sot. 1992,114,9869.69. Stevens, E.D. J.Am. Chem. Sot. 1981,103,5087.70. Summers, J.S; Petersen, J,L, Stolzenberg, Am. J. Am. Chem. Sot. 1994,116,7189.71. Sparks, L.D; Medforth, C.J; Park, M.-S; Chamberlain, J.R; Ondrias, M.R; Senge, M.O; Smith, K.M; Shelnutt,J.A. J.Am Chem.Soc. 1993, 115,581.72. Summers, J.S; Petersen, J.L; Stolzenberg, A.M. J. Am. Chem. Sot. 1994,116,7189.73. DiMagno, S.G; Wertsching, A.K, Ross II, C.R. J.Am. Chem. Sot. 1995,117, 8279.74. Summers, J.S; Petersen, J.h Stolzenberg, A.M. J. Am. Chem. Sot. 1994,116,7189.75, Tse, A.K,-S; Wang, Ru-ji; Mak, T.C.W, Chan, Kin”Shing. Chemical Communications. 1996, 173.76. Scheidt, W.R Ramanuja, J.A. Inorg.Chem. 1975,14,2643.77. Riche, C; Chiaroni, A; Perre-Falwet,M; Gaudemer, A. Acts.Crstaflogr.,Sect.B. 1978,34, 1868.78. Ellison, M.K; Scheidt, W.R. Inorg.Chem.1998, 37,382,79. Godbout, N; Sanders, L.K; Salzmann, R; Havlin, R.H; Wojdelski,M; Oldfield, E; J.Am. Chem.Soc. 1999,121,3829.