Framework Solids Based on Copper(II) Halides (Cl/Br) and Methylene-Bridged Bis(1-hydroxybenzotriazole): Synthesis, Crystal Structures, Magneto-Structural Correlation, and Density Functional Theory (DFT) Studies

A methylene-bridged 1-hydroxybenzotriazole derived ligand L [L = 1, 3-bis(benzotriazol-1-yl)-1,3-dioxapropane] has been synthesized and characterized by spectroscopic and structural methods. Reaction of L with two different copper(II) halides [CuX2; X = Br, Cl] in an identical condition yields two different compounds of similar compositions, {[Cu(mu-Br)(Br)(mu-L)](2)}(n)center dot 2nH(2)O (1) and {[Cu(mu-Cl)(Cl)(mu-L)](2)}(n)center dot 2nH(2)O (2), both being characterized by various physicochemical techniques. Single crystal X-ray studies reveal that they appear as 2D coordination polymers with similar bridging fashion of L. Low temperature magnetic susceptibility measurements reveal antiferromagnetic and ferromagnetic behaviors for 1 and 2 with magnetic coupling constants J = -15.2 and +1.7 cm(-1), which are in a reasonable agreement with their calculated values (J = -9.79 and +0.68 cm(-1) respectively, for 1 and 2). The role of bridging halides in the structure and magnetic properties of the complexes are investigated, and a possible magneto-structural correlation has been established. Influence of spin density of bridging halides on the magnitude of coupling constants has been discussed with the help of density functional theory (DFT) calculations.