This Part 2 of acids and bases illustrates the implementation of the “Research for

the Classroom” program in this 4610/5560 course

• “Research for the Classroom” is a program I am currently implementing as proposed in the Educational Component of my active NSF-CAREER proposal.

• Some classroom students perform a small research project instead of writing a term paper.

• The classroom students’ findings are incorporated into research papers that relate the findings to experimental and computational data in my and my collaborators’ labs or from the literature.

• Three success stories are illustrated here by students in this 4610/5560 class.

M

M

M

N

N

N N

N

N

RR

R

R

R

R

M = Cu; Ag; Au

Metal effect??…

R= e-withdrawing (e.g., CF3)

Should make it a acid

R= e-releasing (e.g., Me; i-Pr; t-Bu)

should make it a base

Project given as a classroom assignment to:

Alex Gonser:

Chem 5560 student in Fall 2003

(in collaboration with his advisor, Dr. Cundari)

DFT-calculated electrostatic potentials mapped on the electron density surfaces of M3Pz3 complexes.Color code: blue=most positive= acidred=most negative= baseYellow = weak base Green = very weak base

Cu3Pz’3 Ag3Pz’3 Au3Pz’3

Pz’ have Me groups on the Pz rings (inductive effect of Me renders all trimers basic)

These triangles are unsubstituted M3Pz3 trimers with M = Cu, Ag, Au

Positive charge

{PzAu}3

-+

-

All strong acids: The inductive effect of CF3 renders all trimers acidic, even the Au trimer. Contrast the following:

{[3,5-(CF3)2Pz]Au}3 {PzAu}3

These findings by Alex combined with

other experimental data led to a paper

just published in Inorganic Chemistry

(the premier journal in inorganic

chemistry) that was selected to be

featured on the JOURNAL COVER…

Trinuclear pyrazolate ring complexes of coinage metals exhibit startling luminescence thermochromism due to intertrimer M-M excimeric bonding in their supamolecular stacks. Though unsubstituted {[Pz]M}3 trimers are bases (Au> Cu >> Ag), fluorination renders even the Au trimer acidic, leading to the isolation of the first acid-base adduct in which a trinuclear AuI complex acts as an acid. See M. A. Omary, M. A. Rawashdeh-Omary, M. W. A. Gonser, O. Elbjeirami, T. Grimes, T. R. Cundari, H, V. K. Diyabalanage, C. S. Palehepitiya Gamage, and H. V. R. Dias, p 8200.

M

M

M

N

N

N N

N

N

RR

R

R

R

R

M= Cu; Ag; Au

Substituent effect:

• R= e-withdrawing (e.g., CF3)

makes it more of a acid

• R= e-releasing (e.g., Me; i-Pr; t-Bu)

makes it more of a base

Metal effect:

Relative basicity: Au>Cu>Ag

Relative acidity: Ag>Cu>Au

SUMMARY

If you want to react with naphthalene ( base), what would you choose for R and M to form an acid-base adduct?

Maha Eldabaja (4610 student here doing research in the Omary group)….just got crystals of an adduct for [Ag(3,5-(CF3)2Pz)]3

with naphthalene and found that it has green emission, consistent with naphthalene phosphorescence

450 500 550 600 650 700

Wavelength, nm

Lu

min

es

ce

nc

e in

ten

sit

y, a

rb. u

nit

s

Maha Eldabaja (4610 student here doing research in the Omary group)….just got crystals of an adduct for [Ag(3,5-(CF3)2Pz)]3

with naphthalene and found that it has green emission, consistent with naphthalene phosphorescence

(let’s hear it for Maha!!)Chi2 : 1.032

Durbin Watson : 1.85

Z : 374.2

Pre-exp. 1 : 825.2 ±1.638E+001

Lifetime 1 : 1.575E+004 s ±6.652E+002

Offset : 26.5

= 15.8 ± 0.7 ms

OK so we studied substituent and M effects, how about the effect of the

bridging ligand itself?

Project THIS SEMESTER for Samer Tekarli

{PzAu}3

{(carb)Au}3 {(im)Au}3

{TzAu}3

{(C6H4)Hg}3

Neutral Anion dH Neutral Anion dH

Carbeniate -33.2603-

32.6385 0.6218 -20871.1756-

20480.9782 390.1973

Imidazolate -39.0693-

38.4402 0.6291 -24516.3538-

24121.5806 394.7731

Pyrazolate -39.0512-

38.4814 0.5698 -24505.0272-

24147.4673 357.5599

Tyrazolate -42.7174-

42.1766 0.5408 -26805.5693-

26466.2027 339.3666

Triphenyl (-1) -37.3825-

36.7372 0.6453 -23457.8726-

23052.9376 404.9350

Triphenyl (-2) -36.7372-

35.8858 0.8514 -23052.9376-

22518.6597 534.2779

Ag

Ag

Au

Au

Cu

Cu

HOMO_1 (54=53)

HOMO_2 (53=54)

LUMO (55)