During transformation of a tetra-nuclear cobalt oxiquinolinate cluster to a deca-nuclear cobalt oxyquinolinate cluster, serendipitous intake of a carbonate ion was observed. By following a similar synthetic path, a deca-nuclear manganese oxyquinolinate cluster was prepared. These clusters show anti-ferromagnetic behavior.
The cocrystals of 2,3-dihydroxynaphthalene with 1,4-diazabicyclo[2.2.2]octane (dabco), hexamethylenetetramine (hmta) and piperazine are studied. The cocrystal 2,3-dihydroxynaphthalene with dabco was obtained as hydrate; it has dihydroxynaphthalene-water chains holding the dabco. Similar piperizine cocrystal is obtained as a methanol solvate, it has piperazine -methanol chains holding the dihydroxynaphthalene molecules through hydrogen bonds and it has also NÀH···p interactions. The cocrystals of hexamethylenetetramine (hmta) with positional isomer 2,7-dihydroxynaphthalene is also studied. The self-assembly of cocrystal of 2,7-dihydroxynaphthalene with hmta utilizes only three nitrogen atoms of the hmta out of four nitrogen atoms to have three moderate hydrogen bonds formed between dihydroxynaphthalene and hmta. Each repeat cyclic sub-assembly has one embraced dihydroxynaphthalene molecule and such molecules are associated with OÀH···p interactions. From DFT-calculations on cocrystals of 2,3-dihydroxynaphthalene with the three amines it is observed that the HOMO are localised on amine unit whereas LUMO are localized in the dihydroxynaphthalene ring. The fluorescence emissions of the cocrystals differ in each case depending on the amine used. NÀH···p interactions of piperazine causes complete quenching of fluorescence emission of diol host enabling it to distinguish from the other two amines.[a] Dr.
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