Blue luminescent zinc(II) complexes with polypyridylamine ligands: crystal structures and luminescence properties

Abstract

A series of blue luminescent zinc(II) complexes, [Zn(dpa)X₂] [dpa = di-2-pyridylamine, X = OAc 1a, Cl 1b, CN 1c or 4-MeC₆H₄S 1d], [Zn(dpa)₂][CF₃SO₃]₂ 2, [Zn(tpda)X₂] [tpda = 2,6-bis(2-pyridylamino)pyridine, X = OAc 3a or Cl 3b] and [Zn(tpda)(CF₃SO₃)₂] 4 has been prepared. Their molecular structures, except complex 4, have been established by X-ray crystallography. In the crystal lattice of 2 the [Zn(dpa)₂]²⁺ cations and CF₃SO₃^– anions are disposed in pairs via intermolecular hydrogen bonds [N(2)  · · ·  O(2) 2.865(4) Å]. The crystal packing of [Zn(dpa)(OAc)₂] 1a revealed that two adjacent molecules associate in pairs through intermolecular hydrogen bonding [N(2)  · · ·  O(4′) 2.816(3) Å]. However, the crystal lattice of its tpda derivative 3a shows that the molecules are linked by extensive intermolecular hydrogen bonding between the amino groups and the acetate ligands [N(2)  · · ·  O(2′) 2.805(3) and N(4)  · · ·  O(4′) 2.860(3) Å] resulting in an interlocking hydrogen bond network. Polymeric one-dimensional tapes are generated through extended π–π stacking interactions between the molecules of [Zn(dpa)(4-MeC₆H₄S)₂] 1d, and the thiolate groups are aligned in an all-anti conformation along the metal chain. In the case of [Zn(dpa)(CN)₂] 1c, co-operative intermolecular hydrogen bonds and aromatic π–π interactions in its solid state lead to a supramolecular two-dimensional sheet. All the zinc(II) complexes display high energy intraligand ¹(π–π*) fluorescence in degassed MeOH at 298 K, and intraligand ³(π–π*) phosphorescence in a glassy solution (MeOH–EtOH 1∶2 at 77 K). An emission band observed for 1c (418 nm) and 1d (481 nm) in their solid state emission spectra is ascribed to excimeric emission due to aromatic π–π interactions.

References

1. A. Kraft, A. C. Grimsdale and A. B. Holmes, Angew. Chem., Int. Ed. Engl., 1998, 37, 402.
2. H. J. Brouwer, V. V. Krasnikov, A. Hilberer and G. Hadziioannou, Adv. Mater., 1996, 8, 935; Y. Kim, S. Kwon, D. Yoo, M. F. Rubner and M. S. Wrighton, Chem. Mater., 1997, 9, 2699.
3. A. Hassan and S. Wang, Chem. Commun., 1998, 211 and refs. therein.
4. (a) M. Fukuda, K. Sawada and K. Yoshino, Jpn. J. Appl. Phys., 1989, 28, L1433; (b) M. Fukuda, K. Sawada and K. Yoshino, J. Polym. Sci. Polym. Chem., 1993, 31, 2465; (c) G. Grem, G. Leditzky, B. Ullrich and G. Leising, Adv. Mater., 1992, 4, 36; (d) see also, D. L. Gin and V. P. Conticello, Trends Polym. Sci., 1996, 4, 217.
5. (a) C.-F. Lee, K.-F. Chin, S.-M. Peng and C.-M. Che, J. Chem. Soc., Dalton Trans., 1993, 467; (b) Y. Ma, H.-Y. Chao, Y. Wu, S. T. Lee, W.-Y. Yu and C.-M. Che, Chem. Commun., 1998, 2491; (c) K.-Y. Ho, W.-Y. Yu, K.-K. Cheung and C.-M. Che, Chem. Commun., 1998, 2101.
6. W. Liu, A. Hassan and S. Wang, Organometallics, 1997, 16, 4257.
7. F. A. Cotton, L. M. Daniels, G. T. Jordan IV and C. A. Murillo, Chem. Commun., 1997, 1673.
8. (a) C.-C. Wang, W.-C. Lo, C.-C. Chou, G.-H. Lee, J.-M. Chen and S.-M. Peng, Inorg. Chem., 1998, 37, 4059; (b) S.-J. Shieh, C.-C. Chou, G.-H. Lee, C.-C. Wang and S.-M. Peng, Angew. Chem., Int. Ed. Engl., 1997, 36, 56; (c) J.-T. Sheu, C.-C. Lin, I. Chao, C.-C. Wang and S.-M. Peng, Chem. Commun., 1996, 315; (d) E.-C. Yang, M.-C. Cheng, M.-S. Tsai and S.-M. Peng, J. Chem. Soc., Chem. Commun., 1994, 2377.
9. J. M. Lehn, Supramolecular Chemistry, 1st edn., VCH, New York, 1995; D. Philp and J. F. Stoddart, Angew. Chem., Int. Ed. Engl., 1996, 35, 1154.
10. D. D. Perrin, W. L. F. Armarego and D. R. Perrin, Purification of Laboratory Chemicals, 2nd edn., Pergamon, Oxford, 1980.
11. PATTY, P. R. Beursken, G. Admirall, W. P. Bosman, S. Garcia-Grauda, R. O. Gould, J. M. Smits, C. Smykalla, The DIRDIF program system, Technical Report of the Crystallography Laboratory, University of Nijmegen, 1992.
12. TEXSAN, Crystal Structure Analysis Package, Molecular Structure Corporation, Houston, TX, 1985 and 1992.
13. SIR 92, Altomare, M. Cascarano, C. Giacovazzo, A. Guagliadi, M. C. Burla, G. Polidori and M. Camalli, J. Appl. Crystallogr., 1994, 27, 435.
14. N. Ray and B. Hathaway, J. Chem. Soc., Dalton Trans., 1980, 1150.
15. J. J. Wolff, Angew. Chem., Int. Ed. Engl., 1996, 35, 2195.