A series of metal–organic frameworks based on polydentate Schiff-base ligands derived from benzil dihydrazone: synthesis, crystal structures and luminescent properties

Abstract

A series of metal–organic frameworks {[AgL1]ClO4}n (1), {[AgL12]BF4}n (2), {[AgL1(NO3)](CH3CH2OH)}n (3), {[ZnL12(NCS)2]CH3CN}n (4), [AgL2(NO3)]n (5), {[FeL22Cl2]·CH3CN}n (6), {[MnL22(NCS)2]·(CH3CH2OH)}n (7) and [ZnL22(NCS)2]n (8) have been synthesized and structurally characterized by IR spectroscopy, UV spectroscopy, thermogravimetric (TG) analyses, luminescent spectroscopy and complete single-crystal structure analyses, where L1 is (N′,N′-bis[1-(pyridin-4-yl)methylidene]benzil dihydrazone) and L2 is (N′,N′-bis[1-(pyridin-3-yl)methylidene]benzil dihydrazone), respectively. The structure of 1 exhibits a two-dimensional layer network featuring trimetal 36-membered non-planar macrocycles. Polymer 2 is a one-dimensional chain structure with tetranuclear metallacyclic rings. For polymer 3, each ligand acts as a bidentate ligand to bind two Ag(I) centers and each silver center is coordinated to two N-donors from two ligands forming a one-dimensional chain. Polymer 4 displays a two-dimensional layer network containing tetranuclear 68-membered metallocyclic rings. Polymers [AgL2(NO3)]n (5), {[FeL22Cl2]·CH3CN}n (6), {[MnL22(NCS)2]·(CH3CH2OH)}n (7) and [ZnL22(NCS)2]n (8) show all one-dimensional chain structures containing bimetallic 8-membered rings and tetrametallic 42-membered rings for 5, bimetallic 34-membered quadrangular rings for 6 and 7, and bimetallic 30-membered quadrangular rings for 8, respectively. The luminescent properties of L1, L2 and 1–8 in the solid state were investigated.