ORIGINAL PAPER

Unusual Very Strong O–H���O Hydrogen Bonding in ZincComplex: Crystal Structure and Photoluminescenceof [Zn(HL)(bpy)2(H2O)]2(L) (L 5 O2C(CF2)6CO2,bpy 5 2,20bipyridine)

Ibrahim Kani

Received: 28 March 2012 / Accepted: 6 June 2012 / Published online: 21 June 2012

� Springer Science+Business Media, LLC 2012

Abstract The centrosymmetric dimer zinc compound,

[Zn(HL)(bpy)2(H2O)]2(L), (L = O2C(CF2)6CO2, bpy =

2,20-bipyridine), was obtained through the reaction of

Zn(ClO4)2�6H2O, bpy and perfluorosuberic acid. Zn(II)

centre is coordinated by four N atoms from two bpy ligands

and two O atoms from a water molecule and monoanionic

suberate ligand in a distorted octahedral coordination

environment. The unit structure contains crystallographi-

cally centrosymmetric suberate anion which acts as a

bidentate bridging ligand between each cationic monomer

complex unit via hydrogen bonding. The very strong

interaction of hydrogen bonding of hydoxycarbonyl–car-

boxylate system in solid state has O–H���O 2.436(3) A

(O���H = 1.25(6) A and H���O = 1.19(6) A). These units

are also connected to each other via p���p, C–H���p, C–F���pand F���F stacking interactions, C–H���O, O–H���O and

C–H���F hydrogen bonds giving rise to a multi-dimensional

network. The complex is the first reported example of a

coordination compound based on both bpy ligands

together with perfluorosuberic acid. Moreover, compound

exhibit intense solid state fluorescent emissions at room

temperature.

Keywords Coordination complex � Perfluorosuberic acid �Symmetrical hydrogen bond � Zinc complex �2,20-Bipyridine

Introduction

The incorporation of transition metal ions and organic

ligands is currently one of the most efficient and widely

utilized approaches toward the construction of metal–

organic coordination architectures [1–3]. To date, numerous

examples of metal–organic frameworks have been con-

structed via covalent interactions [4, 5]. Aside from cova-

lent interactions, hydrogen-bonding contacts are also used

to construct interesting coordination polymers [6, 7].

Hydrogen bonding is an interesting topic that receives much

attention, in terms of aggregation of molecules to advance

some physical properties of supramolecular structures.

Despite the increasing interest, there are many unresolved

problems about the nature of hydrogen bonds. Especially,

controversies are focused on short hydrogen bonds whose

O���O lengths shorter than 2.50 A. The title compound is

novel example of strong symmetric O–H���O type hydrogen

bond. The selection of multi-functional organic ligands,

such as carboxylates, bpy or its derivatives, and mixtures of

both carboxylate and bpy ligands is a key step in the design

and assembly of expected compounds. The coordination

chemistry of saturated linear mono or dicarboxylate anions

[O2C(CH2)nCO2] 2-(n = 1–8) has not been developed and

the structural information for this class of complex is rela-

tively scarce, since it involves the formation of insoluble

polymeric materials, which can be difficult to characterize

and almost impossible to crystallize [8, 9]. A careful

investigation of the Cambridge Structural Database revealed

that no example of coordination polymer or other com-

pounds incorporating a mixture of bpy and perfluorosuberic

acid has been reported. In our previous work, we have iso-

lated mononuclear Co(III) complex, [Co(HL)(phen)2

(H2O)]L�H2O [10], Zn(II) metal organic-frame work, [aqua-

bis(phen)Zn(II)(L)] [11] and polymeric Mn(II) complex

I. Kani (&)

Department of Chemistry, Faculty of Sciences,

Anadolu University, 26470 Eskisehir, Turkey

e-mail: ibrahimkani@anadolu.edu.tr

123

J Chem Crystallogr (2012) 42:832–838

DOI 10.1007/s10870-012-0321-x

{[Mn(L)(phen)2]H2O}n [12] with the mixed ligands (H2L

= HO2C(CF2)8CO2H and phen = 1,10-phenanthroline).

Experimental

Materials and Methods

All chemicals purchased were of reagent grade and used

without further purification. The emission spectra were

recorded on a Perkin-Elmer LS55 fluorescence spectro-

photometer. Elemental analysis for C, H and N were car-

ried out by standard methods.

Synthesis of Zn(II) Complex

A mixture of Zn(ClO4)2�6H2O (0.200 g, 0.54 mmol), bpy

(0.169 g, 1.08 mmol) and 75 % methanol (20 mL) was

stirred for 30 min at 60 �C and then added to perfluoro-

suberic acid (0.419 g, 1.08 mmol); the pH of the resulting

solution was adjusted to 6.0 with aqueous solution of

sodium hydroxide (0.1 mol/L). The mixture was stirred

continuously for 6 h and then filtered. Colorless single

crystals were obtained at room temperature by slow

evaporation of the filtrate over a period of several days

(yield 78 %, based on Mn; m.p. = 183–185 �C.) Analyti-

cal data for complex: C64H38F36N8O14Zn2 (1957.75

g/mol) calcd. C 39.26, H 1.96, F 34.94, N 5.72; found C

39.46, H 1.62, F 34.81, N 5.79.

Caution: zinc and its compounds are toxic and per-

chlorate salts are potentially explosive.

X-ray Crystallography

Diffraction data for the complex were collected with Bru-

ker SMART APEX CCD diffractometer equipped with a

rotation anode at 296(2) K using graphite monochromated

Mo Ka radiation (k = 0.71073 A). Diffraction data were

collected over the full sphere and were corrected for

absorption. The data reduction was performed with the

Bruker SAINT [13] program package. For further crystal

and data collection details see Table 1. Structure solution

was found with the SHELXS-97 [14] package using the

direct-methods and was refined SHELXL-97 [15] against

F2 using first isotropic and later anisotropic thermal

parameters for all non-hydrogen atoms. Hydrogen atom

(H3B) was added to the structure model on calculated

positions and H3A and H7A were refined by least squares.

Geometric calculations were performed with Platon [16].

Table 1 Crystal data and

structure refinement for

complex

Empirical formula C64H38F36N8O14Zn2

Formula weight 1957.8

Temperature 100(2) K

Wavelength 0.71073 A

Crystal system, space group Triclinic, p-1

Unit cell dimensions (A, �) a = 12.5639(4), a = 90.039(2)

b = 12.6374(4), b = 111.482(2)

c = 13.1699(4), c = 112.850(2)

Volume 1768.02(10) A3

Z, Calculated density 1, 1.839 Mg/m3

Absorption coefficient 0.845/mm

F(000) 974

Crystal size 0.44 9 0.25 9 0.15 mm

Theta range for data collection 1.69�–28.53�Limiting indices -16 B h B 12, -16 B k B 16, -17 B l B 17

Reflections collected/unique 25074/8773 [R(int) = 0.0377]

Completeness to theta 28.53–97.7 %

Absorption correction Multi-scan

Max. and min. transmission 0.798 and 0.642

Refinement method Full-matrix least-squares on F2

Data/restraints/parameters 8773/0/568

Goodness-of-fit on F2 1.022

Final R indices [I [ 2r(I)] R1 = 0.0434, wR2 = 0.0945

R indices (all data) R1 = 0.0660, wR2 = 0.1100

Largest diff. peak and hole 0.706 and -0.600 e/A3

J Chem Crystallogr (2012) 42:832–838 833

123

Results and Discussion

Structural Description of [Zn(HL)(bpy)2(H2O)]2(L)

The crystal structure of a new zinc metal–organic framework,

[aqua-bis(2,20-bipyridine)(hydrogenpefluorosuberato)zinc

(II)](1?)(perfluorosuberate), has been constructed from

monoanionic suberate, a water molecule, two bpy and

dianionic suberate ligands. Compound crystallizes in the

triclinic space group P-1 comprise a divalent unique

monocationic Zn(II) central and one independent half-

anion of doubly deprotonated suberate ligand provide the

required 1- charge for complex neutrality (Fig. 1a). The

crystal data, some selected bonds and angles are listed in

Table 1 and 2, respectively. Dianionic suberate bridges two

zinc atoms to from an unusual centrosymmetric dimeric

complex (Fig. 1b). The Zn(II) centre is six coordinated by

four N atoms from two bipy ligands, one aqua ligand and

monocationic Zn(II) center displaying a distorted octahe-

dral coordination environment with the three trans angles

[174.65(9)� for (N1Zn1N4), 166.53(9)� for (O3Zn1N3) and

172.10(8)� for N2Zn1O1)] deviating slightly from the ideal

value of 180�. The Zn–O and Zn–N bond distances and

their relevant bond angles range from 2.1536(19) A to

2.1686(18) A, 2.112(2) A to 2.138(2) A and 77.62(8)� to

174.65(8)�, respectively, values that are within the range of

those observed for other Zn(II) complexes with oxygen or

nitrogen donors [17–19] (Table 2). The bpy ligands are

nearly planar; the interplanar angle between the two pyri-

dine rings is 1.90(2)� and 9.93(2)� A. The endocyclic

Fig. 1 a The molecular structure with 50 % probability displacement ellipsoids and the atom labeling scheme. H atoms are not given except for

7A. Dashed line indicates hydrogen bond. b Unusual centrosymmetric Zn(II) dimer

834 J Chem Crystallogr (2012) 42:832–838

123

torsion angle of the six membered ring (C17C16N4C20) is

-2.1(4)� and (C14C15N3C11) is -1.8(4)�. In the solid-

state structure of complex, the pyridine rings are orientated

at an angle of 98.81(8)� and 89.83(8)� relative to each

other. The stability of complex has gained by this orien-

tation of ligand that lead to minimal nonbonded repulsion

between the atoms as such is a low energy structure. This

orientation would also allow for the best interaction

between the bipy ligand and the metal atom.

It is well known that as hydrogen bonds become shorter

and stronger, the potential will change from an asymmetric

shape to a symmetric double-well shape and ultimately to a

single symmetric flat-bottomed potential [20]. However,

environmental factors can have a very significant effect on

the nature of the hydrogen-bond potential. Carboxylates are

well known to form strong hydrogen bonds. Strong O–HO

hydrogen bonds are defined with O���O separations in the

range 2.50–2.65 A�, and very strong hydrogen bonds with

O���O \ 2.50 A [21]. The latter is rather rare. There is one

reported structure that contains the hydrogen bis(oxamate)

monoanion (the distances are O���O and H���O are 2.466

and 1.233 A, respectively, OHO angle is 180�) [22], where

crystallographic symmetry imposes a symmetric potential

and, in the reported model, the H atom is located centrally.

The other reported structure that contains the ethylammo-

nium oxamate–oxamic acid adduct has the distances of

O���O and H���O are 2.45(2) and 1.225 A, respectively,

OHO angle is 180�) [23]. In the present case, the hydro-

gen bond is in the class of a very strong interaction.

This hydrogen bond is almost symmetric and nonlinear.

The O–H���O hydrogen bond interaction is between car-

boxyl atom O7 and carboxylate atom O5 with O���O =

2.436(4) A (O7���H7A = 1.20(7) A and H7A���O5 =

1.25(7) A), O–H���O = 168.4(7)� (Table 3; Fig. 2). The

striking feature of the title structure is that the complex

entities in the compound are linked together through

hydrogen bonds of the free dicarboxylate acts as a biden-

tate bridging ligand between two cationic zinc units. The

hydrogen bonded carboxylate groups have planer geometry

and the angle between the mean planes is 85.12�.

The crystal structure of molecule is stabilized intermolec-

ular C–H���F and C–H���O, O–H���O C–F���O and F���F inter-

actions (Table 3). The oxygen atom of coordinated water

molecule forms pairs of O–H���O hydrogen bonds with per-

fluorosuberate ion. The oxygen atom (O2) of carboxylate ion

form intra and intermolecular hydrogen bonds, in both case

behave as acceptor, resulting to graph set motif R42(8) as

depicted in Fig. 3 [24–26]. Two strong C–H���F hydrogen

bonds formed two-dimensional chain along b direction

via C18–H18���F11 = 2.53(2) A and C10–H10���F18 =

2.49(4) A which are comparable with reported values of

C–H���F between 2.44 and 2.90 A (Table 2; Fig. 4) [27–29].

The role of F���F contacts in crystal packing is controversial.

Because of the low polarizability of F atoms, it is believed that

the F���F contacts do not stabilize the packing, and fluorine does

not form F���F short contacts which is generally less than 3.0 A

[30]. In the title complex, we observed that F���F interactions

between uncoordinated and coordinated perfluorosuberic acid

Table 2 Bond lengths (A) and angles (�) for complex

Bond lengths (A)

Zn(1)–N(4) 2.112(2)

Zn(1)–N(3) 2.119(2)

Zn(1)–N(1) 2.119(2)

Zn(1)–N(2) 2.138(2)

Zn(1)–O(3) 2.1536(19)

Zn(1)–O(1) 2.1686(18)

F(13)–C(30) 1.350(3)

N(2)–C(10) 1.337(4)

N(2)–C(6) 1.345(3)

C(29)–O(4) 1.204(3)

C(29)–C(30) 1.551(4)

C(6)–C(7) 1.385(4)

C(6)–C(5) 1.478(4)

Bond angles (�)

N(4)–Zn(1)–N(3) 77.67(8)

N(4)–Zn(1)–N(1) 174.65(8)

N(3)–Zn(1)–N(1) 98.81(8)

N(4)–Zn(1)––N(2) 98.23(8)

N(3)–Zn(1)–N(2) 89.83(8)

N(1)–Zn(1)–N(2) 77.62(8)

N(4)–Zn(1)–O(3) 89.34(8)

N(3)–Zn(1)–O(3) 166.53(8)

N(1)–Zn(1)–O(3) 93.90(8)

N(2)–Zn(1)–O(3) 88.52(8)

N(4)–Zn(1)–O(1) 89.27(7)

N(3)–Zn(1)–O(1) 94.21(7)

N(1)–Zn(1)–O(1) 95.04(8)

N(2)–Zn(1)–O(1) 172.10(8)

O(3)–Zn(1)–O(1) 89.09(7)

Table 3 The intermolecular hydrogen bonding geometry (A, �) for

complex

D–H���A D–H H���A D���A \D–H���A

O3–H3B���O2 0.84 1.95 2.722(4) 152.0

O7–H7A���O5 1.20 1.25 2.436(3) 168.4

C20–H20���O3 0.95 2.48 3.066(4) 119.8

C18–H18���F11i 0.95 2.53 3.415(4) 154.0

C10–H10���F18ii 0.95 2.49 3.352(3) 150.4

C3–H3���O7iii 0.95 2.53 3.475(3) 170.6

Symmetry codes: (i) x ? 1, y ? 1, z ? 1; (ii) x ? 2, y ? 1, z ? 1;

(iii) x ? 1, y, z

J Chem Crystallogr (2012) 42:832–838 835

123

through F16–F8 (2.812(12) A) and F13–F6 (2.94(3) A) and

between two coordinated perfluorosuberato ligands via F8–F6

(2.82(12) A). The F���F interactions are similar to reported

values 2.71–2.94 A [31–35] (Fig. 5). In addition, C–H���pinteractions are observed between C13–H13, C14–H14, and

centroid (Cg1) of the C11–C15N3 ring and C17–H17, C18–

H18, and centroid (Cg2) of the C16–C20N4 ring: C13���Cg1 =

3.448 A, H13���Cg1 = 3.650 A, C14���Cg1 = 3.289 A,

H14���Cg1 = 3.398, C17���Cg2 = 3.259 A, H17���Cg2 =

3.520 A, C18���Cg2 = 3.291 A, H18���Cg2 = 3.418 A.

C–F���p interactions are also observed between C18–H18,

C16–F16 and centroid (Cg3) of the C16–C20N4 ring with

F18���Cg3 = 3.264 A, F16���Cg3 = 3.970 A and C3–F3 and

centroid (Cg4) of the C6–C10N2 ring with F3���Cg4 =

3.271 A [36, 37]. Meanwhile the three-dimensional network is

stabilized by p–p stacking interaction which observed between

adjacent bpy ligands (the face-to-face distance is 3.596(4) A).

The p–p interactions are similar to those in the known ana-

logues of Mn, Cu, Zn and Co complexes, with characteristic

interplanar distances between the rings of 3.6 A [38]. The

shortest Zn–Zn distance is 6.712(4) A in the supramolecular

structure.

Fig. 2 Very strong hydrogen-bonding interaction involving hydroxycarbonyl/carboxylate groups in compound

Fig. 3 Hydrogen-bonding pattern involving water/carboxylate groups

Fig. 4 C–F���H contacts in the crystal structure along b direction

836 J Chem Crystallogr (2012) 42:832–838

123

Photoluminescence Properties

Metal–organic frameworks constructed from d10-metal

centers and conjugated organic linkers are promising can-

didates for photoactive materials. Previous studies have

shown that metal complexes containing zinc exhibit pho-

toluminescent properties [39–41]. Therefore, the emission

spectra of Zn(II) complex together with that of the ligands

bpy and perfluorosuberic acid were measured in the solid

state at room temperature. As shown in Fig. 6 the maxi-

mum emission bands for free bipy is at 516 nm (kexc.

359 nm) and for perfluorosuberic acid is at 409 nm (kexc.

293 nm) and 547 nm (kexc. 407 nm). Zinc complex dis-

plays a strong band at 353 nm upon 243 nm excitation. The

fluorescent emissions of the complex can be assigned to

intraligand n–p* and p–p* transitions. Since Zn(II) ions are

difficult to oxidize or to reduce due to their d10 configu-

ration, the emission of the complex is neither ligand-to-

metal charge transfer (LMCT) nor metal-to-ligand charge

transfer (MLCT) [42–44]. However, the complex shows

blue-shift with respect to the free corresponding ligands. It

may derive from the coordination effects of bpy and/or

carboxylic acid to Zn(II) ions, which increases the ligand

conformational rigidity and asymmetry of the ligands,

thereby reducing the non-radiative decay of the intraligand

excited state [45–47].

Conclusion

In summary, we have synthesized a perfluorosuberate-

bridging centrosymmetric dimer Zn(II) complex with bpy

and perfluorosuberic acid ligand. The very strong hydrogen

bonding of carboxylic acid-carboxylate system in solid

state has been reported. The complex shows intense

emissions at room temperature, suggesting that it may be

good candidates for a potential hybrid inorganic–organic

photoactive material.

Supplementary Material

CCDC 834051 contain the supplementary crystallographic

data for this paper. These data can be obtained free of

charge from The Cambridge Crystallographic Data Centre

via www.ccdc.cam.ac.uk/data_request/cif.

Acknowledgments The author is grateful to Anadolu University

and the Medicinal Plants and Medicine research Centre of Anadolu

University, Eskisehir, Turkey, for the use of X-ray Diffractometer.

References

1. Gao J, Wang J, Nie J (2011) Acta Crystallogr C67:m181

2. Wang J, Tao JQ, Xu XJ (2011) Acta Crystallogr C67:m173

3. Kitagawa S, Uemura K (2005) Chem Soc Rev 34:109

4. Phan A, Doonan CJ, Uribe-Romo FJ, Knobler CB, O’Keeffe M,

Yaghi OM (2010) Acc Chem Res 43:58

5. Yaghi OM, Li HL, Davis C, Richardson D, Groy TL (1998) Acc

Chem Res 31:474

6. Jenniefer SJ, Muthiah PT (2011) Acta Crystallogr C67:m69

7. Xu G, Xie Y (2010) Acta Crystallogr C66:m201

Fig. 5 F���F interactions in complex

Fig. 6 Solid-state emission spectra of ligands bpy, HL and complex

at room temperature

J Chem Crystallogr (2012) 42:832–838 837

123

8. Seo J, Matsuda R, Sakamoto H, Bonneau C, Kitagawa S (2009)

J Am Chem Soc 131:12792

9. Kerbellec N, Kustaryono D, Haquin V, Etienne M, Daiguebonne

C, Guillou O (2009) Inorg Chem 48:2837

10. Kani I, Buyukgungor O, Sisman F (2006) Z Nat B 61b:1198

11. Kani I, Sahin O, Yılmaz F, Buyukgungor O (2006) Acta Cryst

E62:m1909

12. Kani I, Darak C, Sahin O, Buyukgungor O (2008) Polyhedron

27:1238

13. Bruker APEX2 (Version 7.23A) and SAINT (Version 7.23A).

Bruker AXS Inc., Madison (2007)

14. Sheldrick GM (2008) Acta Crystallogr A64:112

15. Sheldrick GM (1997) SHELXL-97. Universitat Gottingen,

Gottingen

16. Spek AL (2005) Platon-A multipurpose crystallographic tool.

Utrecht University, Utrecht

17. Chun H, Dybtsev DN, Kim H, Kim K (2005) Chem Eur J 11:3521

18. Sun CY, Dong B, Lv Q, Zheng XJ (2011) Z Anorg Allg Chem

637:276

19. Ye BH, Xue F, Xue GQ, Ji LN, Mak TCW (1999) Polyhedron

18:1785

20. Gilli P, Gilli G (2010) J Mol Struct 972:2

21. Gilli P, Bertolasi V, Ferretti V, Gilli G (1994) Am Chem Soc

116:909

22. Kovalchukova OV, Kuz’mina NE, Zaitsev BE, Strashnova SB,

Palkina KK (2002) Dokl Phys Chem 386:251

23. Price DJ, Fristsch S, Wood PT, Powell AK (2005) Acta Crys-

tallogr E61:m1174

24. Steiner T, Saenger W (1992) Acta Cyrstallogr. B48:819

25. Steiner T, Saenger W (1993) J Am Chem Soc 114:10146

26. Jeffrey GA, Mitra J (1984) J Am Chem Soc 106:5546

27. Dunitz D, Taylor R (1997) Chem Eur J 3:89

28. Lee H, Knobler CB, Hawthorne MF (2000) Chem Commun 2485

29. Bianchi R, Forni A, Pilati T (2003) Chem Eur J 9:1631

30. Bernstein J, Davis RE, Shimoni L, Chang NL (1995) Angew

Chem Int Ed Engl 34:1555

31. Rybalova TV, Yu Bagryanskaya I (2009) J Struct Chem 50:741

32. Ramasubbu N, Parthasarathy R, Murray-Rust P (1986) J Am

Chem Soc 108:4308

33. Bondi AJ (1996) Phys Chem 68:441

34. Dautel OJ, Fourmijue (2000) J Org Chem 65:6479

35. Madjaci NNL, Desiraju GR, Bilton C, Howard JAK, Allen FH

(2000) Acta Cyristallogr. B56:1063

36. Prasanna MD, Guru Row TN (2000) Cryst Eng 3:135

37. Choudhury R, Guru Row TN (2004) Cryst Growth Des 4:47

38. Geraghty M, McCann M, Devereux M, McKee V (1999) Inorg

Chim Acta 293:160

39. Zheng SL, Yang JH, Yu XL, Chen XM, Wong WT (2004) Inorg

Chem 43:830

40. Tao J, Shi JX, Tong ML, Zhang XX, Chen XM (2001) Inorg

Chem 40:6328

41. Chen W, Wang JY, Chen C, Yue Q, Yuan HM, Chen JS, Wang

SN (2003) Inorg Chem 42:944

42. Yersin H, Vogler A (eds) (1987) Photochemistry and photo-

physics of coordination compounds. Springer, Berlin

43. Yang EC, Zhao HK, Ding B, Wang XG, Zhao XJ (2007) Cryst

Growth Des 7:2009

44. Zheng XY, Ye LQ, Wen YH (2011) J Mol Struct 987:132

45. Guo HD, Guo XM, Batten SR, Song JF, Song SY, Dang S, Zheng

GL, Tang JK, Zhang HJ (2009) Cryst Growth Des 9:1394

46. Lu J, Zhao K, Fang QR, Xu JQ, Yu JH, Zhang X, Bie HY, Wang

TG (2005) Cryst Growth Des 5:1091

47. Zhang J, Xie YR, Ye Q, Xiong RG, Xue Z, You XZ (2003) Eur J

Inorg Chem 2572

838 J Chem Crystallogr (2012) 42:832–838

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