Copper(II) halide salts of 5-bromo-2-aminopyridine and 3,5-dibromo-2-aminopyridine: syntheses, structures and magnetic behavior

Abstract

Two 5-bromo-2-aminopyridinium quantum Heisenberg antiferromagnetic (QHAF) complexes of copper(II) have been synthesized and studied structurally and magnetically. The structures of (5-BAPH)2[CuCl4] (1) and (5-BAPH)(3,5-diBAPH)[CuBr4] (2) are reported [5-BAPH = 2-amino-5-bromopyridinium; 3,5-diBAPH = 2-amino-3,5-dibromopyridinium]. Single-crystal X-ray diffraction measurements show that 1 crystallizes in the triclinic space group Pī and 2 crystallizes in the monoclinic space group P21/c. Both products crystallize with a four-coordinate Cu(II) ion and are stabilized with extensive hydrogen bonding between the halide ions and pyridinium and amino substituents on each cation. The tetrahalidocuprate ions in 1 and 2 exist in distorted geometries between square planar and tetrahedral with mean trans angles of 139.48° and 131.85°, respectively. Halogen bonding is also observed. Magnetic susceptibility data were collected on 1 and 2. Magnetic susceptibility data of 1 exhibit moderate antiferromagnetic interactions which are best fit using an alternating chain model [CC = 0.4262(3) cm3 K mol−1, J/kB = −22.75(2) K, α = 0.134(3)]. Magnetic susceptibility data of 2 exhibit weak antiferromagnetic interactions, best fit using a uniform chain model [CC = 0.410(6), J/kB = −6.1(4) K].