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Supramolecular Assembly of Bis(benzimidazole)pyridine: An Extended Anisotropic Ligand For Highly Birefringent Materials
Author(s) -
Thompson John R.,
Ovens Jeffrey S.,
Williams Vance E.,
Leznoff Daniel B.
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201302659
Subject(s) - supramolecular chemistry , birefringence , benzimidazole , hydrogen bond , crystallography , pyridine , chemistry , crystal structure , single crystal , molecule , organic chemistry , optics , physics
Four new bis(benzimidazole)pyridine (BBP)‐containing compounds Zn(BBP)Cl[Au(CN) 2 ], Mn(BBP)[Au(CN) 2 ] 2 ⋅H 2 O, Mn(BBP)Br 2 (MeOH) and Mn(BBP)Cl 2 (MeOH)⋅MeOH have been synthesized and structurally characterized and their birefringence values (Δ n ) determined. The structure of Zn(BBP)Cl[Au(CN) 2 ] contains a hydrogen‐bonded dimer of Zn(BBP)Cl[Au(CN) 2 ] units which propagate into a 1D chain through Au–Au interactions, although the crystals are of poor optical quality. The supramolecular structure of Mn(BBP)[Au(CN) 2 ] 2 ⋅H 2 O forms a 1D coordination polymer through chains of Mn(BBP)[Au(CN) 2 ] 2 units, each containing one bridging Au(CN) 2 and one forming a 2D sheet through Au–Au interactions. The supramolecular structures of Mn(BBP)Br 2 (MeOH) and Mn(BBP)Cl 2 (MeOH)⋅MeOH are very similar, consisting of a complex hydrogen‐bonded network between NH imidazole, methanol and halide groups to align BBP building blocks. In the plane of the primary crystal growth direction, the birefringence values of the three Mn‐containing materials were Δ n =0.08(1), 0.538(3) and 0.69(3), respectively. The latter two birefringence values are larger than in the related 2,2′;6′2′′‐terpyridine systems, placing them among the most birefringent solids reported. These compounds illustrate the utility of extending the π‐system of the building block and incorporating hydrogen‐bonding sites as design elements for highly birefringent materials and also illustrates the effect on the measurable birefringence of the crystal quality, growth direction and structural alignment of the anisotropic BBP building blocks.