Hydro/solvo-thermal syntheses and characterization of a series of Cu-II and Cu-I coordination polymers with an asymmetric semi-rigid Bi-functional ligand: Temperature induced polymorphism and photo-luminescent sensing

摘要

In this work, a flexible asymmetric semi-rigid bi-functional ligand 5-(4-((1H-1,2,4-triazol-1-yl)methyppheny1)1H-tetrazole (HL) has been employed. A series of unique Cu-II and Cu-I coordination compounds, namely [Cu(mu(2)-l)(2)(H2O)(2)](n) (1), [Cu(mu(2)-L)(2)(H2O)(2)](n) (2), [0.1(mu(4)-L)](n) (3) and [Cu-2.5(mu(4)-L)(CN)(1.5)](n) (4), have been prepared under hydro(solvo)-thermal conditions. 1 and 2 present scarcely reported temperature induced polymorphic 1D (1) and 2D (2) copper(II)-L coordination frameworks. When HL and CuBr2 are employed to react in the mixed H2O/ CH3CN (1:1) solvent system, the 3D Cu-I-HL coordination polymer 3 can be isolated. The Cu' centers in 3 should be the reduction of Cu-II ions by CH3CN solvent. When CuBr is used to replace CuBr2 under similar synthetic conditions of 3, 4 can be isolated. 4 is a unique 3D Cu' cluster-based coordination framework assembled from L- and CN-. PXRD patters of all the bulky samples 1-4 also have been determined, which agree well with theoretical PXRD patterns, confirming pure phases. Photo-luminescent measurements also show that complexes 3-4 can behave highly sensitive photo-luminescent sensing of small solvent molecules DMF and NMP. Additionally, 4 also exhibits highly selective and sensitive photo-luminescent discriminating of dichromate anions in aqueous solutions with excellent quenching efficiency (K-sv = 2.38 x 10(4) L mol(-1)). The experiment result also demonstrates the broad prospects in the preparation of these novel coordination frameworks using these flexible bifunctional asymmetric semi-rigid ligands as basic building blocks.