Two new coordination compounds involving hexanuclear Cu(ii), viz, [Cu6(phen)6(μ4-adpt)4(H2O)2](NO3)4·10H2O (1) and polymeric Co(ii), viz, {[(μ2-adpt)4Co(μ2-H2O)2Co(H2O)4]·4H2O}n (2) (phen = 1,10-phenanthroline; adpt = adipate) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (IR, electronic and ESR), PXRD and single crystal X-ray diffraction techniques Discrete nitrate-water clusters involving the [(H2O)3NO3]- core in 1 and linear (H2O)4 core in 2 provide stability to the layered network of the structures of the compounds Interestingly, the water clusters in polymer 2 are encapsulated as guests in the voids of the host square grid that extends in 2D architecture Theoretical studies have revealed the presence of interesting energetically significant cooperativity effects of π-stacking contacts that are responsible for the hexanuclear structure of compound 1 Both complexes significantly inhibit cell viability by inducing apoptotic cell death in the DL cancer cell line with negligible cytotoxicity in normal cells (PBMC) An assessment of ROS (reactive oxygen species) level study revealed a rapid increase of ROS in DL cells indicating cytotoxicity of the compounds against the DL cells A decrease in MMP (mitochondrial membrane potential) is associated with an opening of the mitochondrial permeability transition pores which corroborates the apoptotic features of 1 and 2 The mode of action of the cytotoxic activities of the compounds has been explored with respect to their in silico docking ability and further inhibition of antiapoptotic proteins as evidenced by western blot analysis SAR analyses based on pharmacophore modelling reveal that the molecular features of the structures of the compounds play important roles in biological activities

Adipato bridged novel hexanuclear Cu(II) and polymeric Co(II) coordination compounds involving cooperative supramolecular assemblies and encapsulated guest water clusters in a square grid host: antiproliferative evaluation and theoretical studies

Two new isostructural coordination compounds of cobalt(II) and zinc(II) involving 1,10-phenanthroline and 2,5-pyridine dicarboxylate, viz., [Co(2,5-PDC)(phen)2]·9H2O (1) and [Zn(2,5-PDC)(phen)2]·9H2O (2) (in which, PDC = pyridine dicarboxylate, phen = 1,10-phenanthroline) have been synthesized and characterised using FT-IR, electronic spectroscopy, thermal analysis, elemental analysis and single crystal X-ray diffraction techniques. Crystal structure analysis reveals that the neighboring monomeric units of 1 and 2 are self-assembled via π-stacking, C–H⋯π and C–H⋯O interactions. Fascinating and unusual discrete (H2O)21 clusters in 2 stabilize the network architecture. The self-assembled enclathration of water clusters in the hexameric supramolecular host cavity of 1 provides additional reinforcement to the crystal structure. The strength of the biologically relevant cooperative π-stacking interactions for 1 and 2 has been investigated using DFT calculations and analyzed using an NCI plot index. Remarkably, the (π–π)1 binding modes in the ternary π-stacked assemblies are energetically more significant than the (π–π)2 mode due to the contribution of the two symmetrically related C–H⋯O interactions. The large and almost identical dipole moments of the compounds nullify the influence of the metal centers on the strength of the cooperative π-stacked assemblies, and this corroborates the strong binding energies. The compounds significantly induce concentration dependent cell cytotoxicity and apoptosis in DL cancer cells with negligible cytotoxicity in normal cells. The molecular docking study and pharmacophore features establish the structure activity relationship (SAR) of the compounds.

Biologically relevant and energetically significant cooperative ternary (π–π)2/(π–π)1/(π–π)2 assemblies and fascinating discrete (H2O)21 clusters in isostructural 2,5-pyridine dicarboxylato Co(II) and Zn(II) phenanthroline compounds: antiproliferative evaluation and theoretical studies

Energetically significant cooperative π-stacked ternary assemblies in Ni(II) phenanthroline compounds involving discrete water clusters: Anticancer activities and theoretical studies

Synthesis and solid state self-assembly of a 1,4-diazepine derivative: Water cluster as molecular glue and conformational isomerism

Water cluster encapsulated polyoxometalate (POM)-based hydrogen-bonded supramolecular frameworks (PHSFs) are novel advanced high-capacity electrode materials for supercapacitors thanks to synergistic effects from internal components as well as the existence of numerous electronic transports and proton conductive pathways formed by hydrogen bond interactions. In this work, three new water cluster encapsulated PHSFs: [Cu2(H2O)4H2(imbta)4](PMo12O40)2·6H2O (1), [Cu (H2O)2H4(pybta)4](PMo12O40)2·2H2O (2) and [Ag2H7(pybta)6(PMo12O40)3]·12H2O (3) as well as one new PHSF: [AgH2(imbta)2](PMo12O40) (4) were hydrothermally synthesized, where the imbta and pybta are 1-imidazol-1-ylmethyl-1H-benzotriazole and 1-pyridin-3-ylmethyl-1H-benzotriazole, respectively. The electrochemical properties of the four compound-based electrodes were estimated by cyclic voltammetry, galvanostatic charge-discharge, electrochemically active surface area, and electrochemical impedance spectroscopy. In particular, due to the unique water-cluster-encapsulated PHSF structure with a large number of O–H⋯O interactions, the 1-based electrode has the highest specific capacitance of 710 F·g−1 at 1 A·g−1 among all the four electrodes, which is superior to that of most POM-based electrodes to date. Furthermore, the 1-based electrode exhibits an excellent capacitance retention about 91.2 % after 1000 cycles at a high charge/discharge current density of 10 A·g−1. The results of this study provide inspiration and guidance for the construction of PHSF-based electrode materials, which have broad application potential in a new-generation of high-performance energy storage devices. 

Water cluster encapsulated polyoxometalate-based hydrogen-bonded supramolecular frameworks (PHSFs) as a new family of high-capacity electrode materials

Three crystalline complexes containing fluorine anion water clusters, [Cd(Im)6][F·H2O]2 (1), [Ni(Im)6][F2·(H2O)5] (2) and [Co(Im)6][F·NO3·(H2O)4] (3), were reported. The interesting fluorine anion water clusters are described in this paper. Single X-ray analysis shows that fluoride ions in the water clusters have different coordination environments, four-coordinated in a tetrahedral geometry for (1), five-coordinated in a trigonal bipyramidal geometry for (2), and three-coordinated in a planar trigonal geometry for (3). F−(H2O)n is assembled by strong H-bonding interactions [OH⋯F = 2.576(1)–2.813(1) A], where a fluoride anion plays an important role in connecting an imidazole ligand of the host [M(Im)6]2+. The strength of an ionic bond between the host and guest is strongly influenced by the F−(H2O)n water cluster adjacent to the ligand with NH⋯F distances of 2.607–2.755 A. The TGA, IR and XRD studies for the above three compounds at different testing temperatures suggested that the fluorine anion water cluster, F−(H2O)n, was very stable. This result distinctly differentiates these compounds from the reported ones containing neutral water cluster molecules. This phenomenon indicated the stronger anionic hydrogen-bond interaction between F− and H2O, which also confirmed the intracluster proton transfer process F−·H2O → HF·OH−. This result suggests that the fluorine anions and water molecules are H-bonded to each other in an alternating fashion within the fluoride−water hybrid cluster, where a fluorine anion plays the important role of connecting the host metal complex and guest water cluster.

Interesting fluorine anion water clusters [F−·(H2O)n] in metal complex crystals

A well chloride−water cluster [Cl6(H2O)8]6− in the complex [Cu3(DMAP)12Cl6•8H2O] (DMAP = N,N’-dimethyl p-aminopyridine) has been investigated structurally in the solid state The chloride-water cluster [Cl6(H2O)8]6− is stabilized and orderly arranged by hydrogen bonds which display high symmetry Six hosts [Cu(DMAP)4]2+ cationic form a cage-like aggregation, and chloride-water [Cl6(H2O)8]6− cluster located in the cage Cl− anion play an important role to connect cubane-like (H2O)8 water cluster forming [Cl6(H2O)8]6− cluster, and on the other hand, to connect cage-like [Cu(DMAP)4]2+ cationic aggregation by means of ionic electrostatic interaction and long-range coordinate bond interaction The formation of such a cluster anion may be available for insight into the nature of hydration of chloride in H2O

Encapsulation of Chloride-water cluster anion [Cl6(H2O)8]6- in a cage structure based [Cu(DMAP)4]2+ aggregation

Using Ni(Im)62+ (Im = imidazole) as the structural unit, the effects of oxygen-containing anions, such as SO42-, NO3− and CO32- on the structure of water clusters were studied. The crystal structur...

E Liu

Papers

Interesting fluorine anion water clusters [F−·(H2O)n] in metal complex crystals

Encapsulation of Chloride-water cluster anion [Cl6(H2O)8]6- in a cage structure based [Cu(DMAP)4]2+ aggregation

Effects of different oxygen-containing anions on the structure of water clusters