An adaptable heterometallic trinuclear coordination cluster in the synthesis of tailored one-dimensional architecture: structural characterization, magnetic analysis and theoretical calculations

Abstract

A new trinuclear complex [(CuL^α-Me)₂Co(bnz)₂] (1) has been synthesized by using a metalloligand [CuL^α-Me] (H₂L^α-Me = N,N′-bis(α-methylsalicylidene)-1,3-propanediamine, bnz = benzoate) with trans-coordinated syn–syn bridging benzoate group (1κO:2κO′). The syn–syn coordinative selectivity of carboxylate towards this trinuclear unit leads exclusively to the formation of linear coordination cluster. Such coordinative adaptability is exploited for supramolecular assembly using a dicarboxylate linker, terephthalate (tph, 1,4-benzenedicarboxylate) which yielded a tailored one-dimensional quasi-linear coordination polymer [(CuL^α-Me)₂Co(tph)]_n•2nH₂O (2) having the linear trinuclear node. Isothermal magnetization measurement at 2 K suggests that both 1 and 2 posses S = 1/2 ground spin state indicating the presence of antiferromagnetic coupling at low temperature. The variable-temperature magnetic susceptibility measurements also reveal that both compounds are antiferromagnetically coupled with exchange coupling constants (J) of −17.3 and −9.2 cm⁻¹ for 1 and 2, respectively. The nature and magnitude of exchange interactions are further corroborated by density functional calculations.