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

Three new 3D metal-organic frameworks, namely {[Zn(L)(2)]}(n) (2), {[Cu(L)3H(2)O]3H(2)O}(n) (4), and {[Ag(L)]3H(2)O}(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 Zn-II, Cu-II, and Ag-I salts under similar experimental conditions. By introducing the secondary ligand terephthalic acid (H(2)bdc), another two new compounds {[Zn1.5L2(bdc)(0.5)]3H(2)O}(n) (1) and {[Cu(L)(bdc)(0.5)H2O]}(n) (3) with different 3D structures were obtained. Compound 1 possesses a three-fold interpenetrating framework, with {3(2).4(2).5(4).6(2)}(2){3(2).4(2).5(6).6(5)} 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 pi-pi* transition.