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A new hybrid inorganic-organic compound [Cu(Hdien)2(H2O)2](pnb)4·4H2O (1) (where pnb = p-nitrobenzoate), in which the tridentate ligand diethylenetriamine (dien) shows an unusual coordination behavior acting as a bidentate ligand when present in its monoprotonated form (Hdien+) has been synthesized by the reaction of copper(II) p-nitrobenzoate and slight excess of dien in methanol-water mixture (4:1v/v). Re-crystallization of the violet precipitated product from hot water gave single crystals suitable for X-ray diffraction studies. The newly synthesized compound 1 has been characterized by spectroscopic techniques (UV–Vis, FT-IR, EPR), and theoretical methods (DFT and MRCI/SORCI). Single crystal X-ray structure determination revealed the existence of the cationic species [Cu(Hdien)2(H2O)2]4+, four p-nitrobenzoate as counter anions and four water molecules are present as solvent of crystallization. Packing analyses of title compound as well as of the structurally similar [Cu(en)2(H2O)2](pnb)2, 2 has shown similarities in the crystalline architecture that both hybrid inorganic-organic compounds is stabilized by various non-covalent interactions such as N-H⋯O, C-H⋯O, O-H⋯O etc.

The solid-state supramolecular structure of 6-methylisocytosine dihydrogen monophosphate adduct ½2-NH2-6-CH3-C4H2N2O2� þ 2 � H2PO � 4 , has been determined by single-crystal X-ray diffraction at room temperature. In this paper a revised model, based on single proton transfer from one molecule of phosphoric acid to the pyridine N atoms opposite to the methyl substituent of the two aminooxo tautomers of 6methylisocytosine, has been used for the crystal structure analysis of the ionic complex. 6-Methylisocytosine molecules form hemiprotonated centrosymmetric pairs by complementary WC triple hydrogen bonds. Dihydrogen phosphate anions act as bridges between charged WC dimers to generate ribbons via four cation-to-anion N–H ��� O hydrogen bonds. Ribbons are then interconnected to form a threedimensional network by means of a further series of O–H ��� O anion-to-cation hydrogen bonds.