Syntheses, molecular and supramolecular structures, and magnetic properties of a mononuclear Mn II and a dicyanamide-bridged one-dimensional Cu II compound derived from enolic 4-terpyridone

Abstract

Syntheses, molecular and supramolecular structures, and magnetic properties of a mononuclear manganese(II) compound [Mn II(LH) 2](ClO 4) 2 ( 1) and a dicyanamide-bridged one-dimensional copper(II) compound [Cu II(LH)(μ 1,5-dca)] n (NO 3) n ( 2) derived from enolic 4-terpyridone (LH) have been described. The compounds 1 and 2 crystallize in monoclinic P 2 ( 1 ) / n and triclinic P 1 ¯ space groups, respectively, with the following unit cell parameters – 1: a = 8.8281(4) Å, b = 8.7736(4) Å, c = 39.7838(16) Å, β = 95.719(1)°, and Z = 4; 2: a = 7.5342(3) Å, b = 8.9307(4) Å, c = 15.0189(8) Å, α = 73.0032(15)°, β = 81.3701(16)°, γ = 65.461(2)°, and Z = 2. In 1, the metal center is hexacoordinated by three pyridine nitrogens of each of the two enolic 4-terpyridones. In 2, the metal center is pentacoordinated by three pyridine nitrogens of 4-terpyridone and two nitrogens of two end-to-end (EE; μ 1,5-) dicyanamide. The coordination geometries of 1 and 2 are distorted octahedral and distorted square pyramidal, respectively. Eight hydrogen bonds, six of C–H⋯O types and two of O–H⋯O types, link the complex cation [Mn II(LH) 2] 2+ and two perchlorate anions into a three-dimensional network in 1. In the case of 2, seven hydrogen bonds, six of C–H⋯O types and one of O–H⋯O type, link the dicyanamide-bridged one-dimensional chains into a two-dimensional sheet consisting of interlinked one-dimensional double-chains. It may be noted that O–H group of enolic 4-terpyridone participates in hydrogen bonding interactions and in developing extended structures in both 1 and 2. Variable-temperature (2–300 K) magnetic susceptibility measurements of both the compounds have been performed to understand the possibility of spin transition in 1 and exchange interaction in 2. However, the susceptibility data of 1 indicate the existence of high-spin manganese(II) throughout the temperature range. In the case of 2, copper(II) centers are noninteracting which is related to the highly distorted coordination geometry of the metal ion.