Abstract
Six coordination compounds: [Li(H2O)4]+·hmta·Cl−, [Li(H2O)4]+·hmta·I−, [Na(H2O)4(hmta)] 2 2+ ·2H2O·2Br−, [Na(H2O)4(hmta)] 2 2+ ·2H2O·2I−, [K(H2O)(hmta)I] n and [Rb(H2O)(hmta)I] n , have been synthesized and characterised by IR spectroscopy, thermogravimetry coupled with differential thermal analysis, elemental analysis and X-ray crystallography. Both the sodium compounds are isostructural in a solid state, an isostructurality is also observed between compounds containing potassium and rubidium iodides. The sodium compounds exist as dimers (dinuclear core of the complex ion is created by two sodium cations and two water molecules). The molecules of potassium and rubidium compounds are assembled to the two dimensional hybrid nets. The each potentially multifunctional ligand (the hmta) exists in the outer coordination sphere in lithium compounds, acts in a monodentate mode in sodium compounds and in bidentate-bridging modes in potassium and rubidium compounds. The lithium ions are four coordinated, and the sodium, potassium and rubidium ions are six coordinated. Thermal analyses show that the investigated compounds decompose gradually with the formation of alkali metal halides which, during the further heating, are totally removed or they undergo partial decomposition to oxides.
Highlights
The alkali metal ions play important roles in biological systems, for example they incorporate into important biological molecules such as enzymes [1] proteins and peptides [2,3,4], nucleotides [5] and membrane lipids [6]
Both the sodium compounds are isostructural in a solid state, an isostructurality is observed between compounds containing potassium and rubidium iodides
Each lithium cation is four coordinated by the four oxygen atoms of water molecules, each sodium cation is six coordinated by one monodentate hmta molecule, three terminal water molecules and two bridging water molecules, and the potassium and rubidium cations are six coordinated by two bridging bidentate hmta molecules, two bridging iodide ions and two bridging oxygen atoms of water molecules
Summary
The alkali metal ions play important roles in biological systems, for example they incorporate into important biological molecules such as enzymes [1] proteins and peptides [2,3,4], nucleotides [5] and membrane lipids [6]. Is of the utmost importance because of their significant role in different biological processes [19, 20] especially in the cell biology [21] and natural fluids biochemistry [22, 23]. For example potassium and sodium, together with proteins switching ion channels, are responsible for maintenance of the ionic equilibrium and these cations availability in intercellular fluids are responsible for electrochemical gradients across cell membranes and in consequence for transmitting nerve impulses and regulation of cell functions [21]. An increasing interest is put on construction of dinuclear, multinuclear and polymeric coordination compounds [24,25,26,27] created by self-assembly [28] of the components [29,30,31,32]
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