Synthesis, characterization and thermal studies of 1,3-bis(4-pyridyl)propane bridged dicobaloximes

•Twelve different 1,3-bis(4-pyridyl)propane-bridged dicobaloximes have been reported.•TGA, DTA and DSC studies were carried out in order to know the thermal stability and phase transition.•DSC study of these complexes with long alkyl chain reveals two mesomorphic phases.•X-rd study reveal that in the present systems two Co(dmgH)2 are not equivalent.•Crystal packing diagram indicates the presence of extensive intermolecular interactions.

Twelve different 1,3 bis(4-pyridyl)propane (dpyp)-bridged dicobaloximes of the type [RCo(dmgH)2]2-μ-1,3-bis(4-pyridyl)propane where R = Me – octyl (1a–8a), decyl (9a), dodecyl (10a), tetradecyl (11a), 1-chlorohexyl (12a) have been synthesized from their corresponding aqua complexes. All the synthesized cobaloximes have been characterized by 1H, and 13C Nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, UV–visible (UV–Vis) and FT-IR spectroscopy. The X-ray structures of 2a and 8a are reported. Thermal stability of these complexes has been studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Differential scanning calorimetry (DSC) study reveals that there is a mesophase in these ligand-bridged dicobaloximes with higher alkyl chains. These dpyp-bridged complexes are significant due to the flexible spacer of dpyp in between two cobaltmetallobicycles which influence extensive intermolecular CH⋯O interactions in the crystal packing diagram of the structures 2a and 8a. The mesophase formation for these complexes strongly depends on the length of the alkyl chain (axial R group).

Graphical abstractWe report the synthesis of twelve different 1,3 bis(4-pyridyl)propane (dpyp) bridged dicobaloximes of the type [RCo(dmgH)2]2-μ-1,3-bis(4-pyridyl)propane. The X-ray structure of 2a and 8a are reported. TGA/DTA analysis shows that these complexes are stable as compared to the reported cobaloxime complexes. Crystal packing diagram of this compound shows the presence of extensive intermolecular CH⋯O interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide