Structural Diversity and Properties of Five 3D Metal–Organic Frameworks Based on a Pyridine-substituted Triazolyl Benzoate Ligand

Abstract

Three new 3D metal–organic frameworks, namely {[Zn(L)2]}n (2), {[Cu(L)3H2O]3H2O}n (4), and {[Ag(L)]3H2O}n (5) where HL = 4-[3-methyl-5-(pyridin-4-yl)-1,2,4-triazol-4-yl]benzoate, have been synthesized by reaction of the HL ligand and ZnII, CuII, and AgI salts under similar experimental conditions. By introducing the secondary ligand terephthalic acid (H2bdc), another two new compounds {[Zn1.5L2(bdc)0.5]3H2O}n (1) and {[Cu(L)(bdc)0.5H2O]}n (3) with different 3D structures were obtained. Compound 1 possesses a three-fold interpenetrating framework, with {32.42.54.62}2{32.42.56.65} topology. To the best of our knowledge, 2 is an unusual example of four-fold framework guest-free metal organic framework material. Compound 3 reveals a seven-connected ose topology; magnetic susceptibility measurements indicate that it has dominating antiferromagnetic couplings between metal centres. Photoluminescence measurements of 1, 2, and 5 in the solid state at room temperature show that all coordination networks exhibit a red shift in the emission spectra, which can be assigned to an intraligand π-π* transition.