A series of Cd(II) complexes with π–π stacking and hydrogen bonding interactions: Structural diversities by varying the ligands

Seven new Cd(II) complexes consisting of different phenanthroline derivatives and organic acid ligands, formulated as [Cd(PIP)2(dnba)2] (1), [Cd(PIP)(ox)]·H2O (2), [Cd(PIP)(1,4-bdc)(H2O)]·4H2O (3), [Cd(3-PIP)2(H2O)2]·4H2O (4), [Cd2(3-PIP)4(4,4′-bpdc)(H2O)2]·5H2O (5), [Cd(3-PIP)(nip)(H2O)]·H2O (6), [Cd2(TIP)4(4,4′-bpdc)(H2O)2]·3H2O (7) (PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline, 3-PIP=2-(3-pyridyl)imidazo[4,5-f]1,10-phenanthroline, TIP=2-(2-thienyl)imidazo[4,5-f]1,10-phenanthroline, Hdnba=3,5-dinitrobenzoic acid, H2ox=oxalic acid, 1,4-H2bdc=benzene-1,4-dicarboxylic acid, 4,4′-H2bpdc=biphenyl-4,4′-dicarboxylic acid, H2nip=5-nitroisophthalic acid) have been synthesized under hydrothermal conditions. Complexes 1 and 4 possess mononuclear structures; complexes 5 and 7 are isostructural and have dinuclear structures; complexes 2 and 3 feature 1D chain structures; complex 6 contains 1D double chain, which are further extended to a 3D supramolecular structure by π–π stacking and hydrogen bonding interactions. The N-donor ligands with extended π-system and organic acid ligands play a crucial role in the formation of the final supramolecular frameworks. Moreover, thermal properties and fluorescence of 1–7 are also investigated.

Graphical abstractSeven new supramolecular architectures have been successfully isolated under hydrothermal conditions by reactions of different phen derivatives and Cd(II) salts together with organic carboxylate anions auxiliary ligands.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Complexes 1–7 are 0D or 1D polymeric structure, the π–π stacking and H-bonding interactions extend the complexes into 3D supramolecular network. To our knowledge, systematic study on π–π stacking and H-bonding interactions in cadmium(II) complexes are still limited. ► The structural differences among the title complexes indicate the importance of N-donor chelating ligands for the creation of molecular architectures. ► The thermal and fluorescence properties of title complexes have also been reported.