Dimeric and Monomeric Cu(II) 2,2'-bipyrimidine dicarboxylates in distorted environments: Structural Diversity, Magneto- Structural Correlations and Additives in Thermolysis of Ammonium Nitrate

Abstract

Two new copper(II) compounds, dimeric [Cu sub(2)(fum)(bpm) sub(2)(H sub(2)O) sub(2)(NO sub(3)) sub(2)] 1 and monomeric [Cu(ida)(bpm)].4H sub(2)O 2 from rigid (fum sup(2-)) and flexible (ida sup(2-)) dicarboxylates were structurally characterized as undergoing Jahn- Teller tetragonal distortions (Z- out) to form distorted square-based pyramidal geometries (0 less than torque 5 less than 1) forming a herring- bone (1) and columnar supramolecular motifs (2). Wavefunction and molecular orbital analysis for 1 and 2 revealed strong in- plane Pi- covalency (K// less than K┴ and g// less than or equal to 2.3) with Z- out elongation and significant nephelauxetic electron delocalization. For 2, the bonding parameter hierarchy: Alpha 2 (0.741) less than beta 12 (0.860) less than beta 2 (1.066) verified a highly anisotropic, distorted coordination geometry defined by strong, cooperative in- plane sigma and Pi- bonding interactions alongside a stable, weakly mixed out- of- plane Pi- network driven by subtle orbital adjustments. EPR and magnetic studies confirmed that the unpaired electron resides in the dx sup(2)-y sup(2) orbital, revealing the coexistence of weak ferromagnetic and antiferromagnetic interactions (phi=+ 5.504 and J=-13.7 cm sup(-1)) for dimeric 1 and 2 behaving as a simple monomeric paramagnet. Thermogravimetric and Kinetic modeling (Coats- Redfern) presented positive Delta H and Delta G values affirming a non- spontaneous endothermic process of AN decomposition by 1 and 2, with lower activation energy. Thus, warranting the role of 1 and 2 as effective, low temperature additives for the thermolysis of AN via the ionic pathway.