Hybrid materials based on transition metal–BTC–benzimidazole: solvent assisted crystallographic and structural switching

Abstract

Five transition metal–BTC–BIm based coordination polymers, namely [Zn₂(HBTC)₂(BIm)₂(H₂O)₂]·(H₂O)₃, 1; [2-HABI]₂[Zn₂(BTC)₂(2-ABI)(H₂O)]·(H₂O)₅, 2; [Cu₃(BTC)₂(BIm)₆][solvent], 3; [Co₄(BTC)₃(BIm)₆][solvent], 4; and [(CH₃CH₂)₂NH₂][Zn(BTC)(BIm)]·(H₂O), 5 have been synthesized and characterized using complementary techniques like single crystal X-ray analysis, powder X-ray diffraction (PXRD) and thermogravimetric analysis (TGA) (BTC = 1,3,5-benzene tricarboxylic acid, BIm = benzimidazole and 2-ABI = 2-aminobenzimidazole). Crystal structure analysis of these compounds showed that 1 forms a 1D chain, 2 and 3 have 2D layers while 4 and 5 have three-dimensional architectures. 3 forms a hexagonal bronze sheet, 4 has a three-dimensional network with embedded paddlewheel SBUs and helical assembly, and 5 crystallizes in a polar space group (Pna2₁) with 3D helical networks with adamantane-type topology. The dielectric properties of 5 showed that the dielectric constant rapidly decreases with an increase in frequency suggesting dipole relaxation at low frequencies.