Supramolecular Assembly of Bis(benzimidazole)pyridine: An Extended Anisotropic Ligand For Highly Birefringent Materials

Abstract

Four new bis(benzimidazole)pyridine (BBP)-containing compounds Zn(BBP)Cl[Au(CN)2], Mn(BBP)[Au(CN)2]2·H2O, Mn(BBP)Br2(MeOH) and Mn(BBP)Cl2(MeOH)·MeOH have been synthesized and structurally characterized and their birefringence values (Δn) 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·H2 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)Br2(MeOH) and Mn(BBP)Cl2(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 Δn=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.

Correlating Structural Features and 207Pb NMR Parameters with the Stereochemical Activity of PbII Lone Pairs in Birefringent Pb[2,6‐bis(benzimidazol‐2‐yl)pyridine] Complexes

“…The magnitude of Δ n was determined by optical microscopy for all compounds at 546 nm; the results are summarized in Table . Consistent with previous studies of bbp complexes,, all the crystals are highly birefringent, with values ranging from 0.31(5) for Pb(H 2 O)(bbp) 2 [Au(CN) 2 ] 2 to 0.660(4) for [Pb(bbp)Br 2 ] · 2H 2 O. This wide range of observed Δ n values reflects differences in the orientation of the bbp ligands and the viewing direction during the experiment.…”

“…Birefringence (Δ n ) arises when the refractive index varies depending on the direction of light propagation through a crystal, and can be traced to the anisotropic arrangement of the atoms and molecules within the material , . The magnitude of birefringence depends on a number of factors, including the polarizability anisotropy of the building blocks (which is high for bbp), the orientation of these components within the lattice and the crystal‐growth habit , . The magnitude of Δ n was determined by optical microscopy for all compounds at 546 nm; the results are summarized in Table .…”

“…This wide range of observed Δ n values reflects differences in the orientation of the bbp ligands and the viewing direction during the experiment. In the case of [Pb(bbp)Br 2 ] · 2H 2 O, which is amongst the most birefringent compounds known, bbp ligands adopt a favourable parallel alignment and are oriented in a near optimal direction with respect to the viewing direction , …”

Structures and Fluorescent Properties of Cadmium(II) Complexes with 1D and 2D Structures Based on Tridentate Benzimidazole Ligands

“…[14,15] The investigation concerned with the construction of supramolecules by using tridentate ligands containing benzimidazoles is still limited though these ligands can be used as multifunctional building blocks. [16,17] The ligands 2,6-bis(benzimidazol-2-yl)pyridine (L1) and bis(2-benzimidazolylmethyl)amine (L2) consist of two benzimidazole moieties and can act as tridentate chelating ligands. L1 has a rigid and nearly planar structure, in which the two benzimidazole groups are attached to the 2,6 position of a pyridine ring.…”

Thin Films of Tolane Aggregates for Faraday Rotation: Materials and Measurement

“…Traditionally the field of magneto-optics has been dominated by inorganic materials or radical species [5][6][7][8]. Only recently have diamagnetic organic materials emerged as novel FR supplies [9][10][11][12][13][14].…”