Synthesis and crystal structure of a silver(I) 6-methylmercaptopurine riboside complex.

Silver nitrate reacts with 6-methylmercaptopurine riboside (6-MMPR) in aqueous solution containing methanol and dimethyl sulfoxide at room temperature to give a colourless crystalline complex, namely, bis(6-methylmercaptopurine riboside-κN7)(nitrato-κ2O,O')silver(I) 2.32-hydrate, [Ag(NO3)(C11H14N4O4S)2]·2.32H2O. The crystal structure, determined from synchrotron diffraction data, shows a central AgI ion on a crystallographic twofold rotation axis, coordinated in an almost linear fashion by two 6-MMPR ligands via atom N7 (purine numbering), with the nitrate counter-ion loosely coordinated as a bidentate ligand, forming a discrete molecular complex as an approximate dihydrate. The complex and water molecules are connected in a three-dimensional network by hydrogen bonding.

Analytical study to determine the optical properties of gold nanoparticles in the visible solar spectrum.

In this work the optical properties of the formed gold nanoparticles, that obtained upon reducing the gold(I):6-thioguanosine hydrogel by dimethylamine borane (DMAB) have been studied. The analytical measurements to calculate the optical band gap showed a significant narrowing in the optical band gap value (Eg). Tauc plot was used to estimate the optical band gap (Eg) with the direct and indirect allowed transitions, before and after the reducing process. Narrowing the band gap is very important to increase the efficiency of the semiconductor material as it leads to absorbing in the visible region of the solar spectrum.

Circularly polarised luminescence in an RNA-based homochiral, self-repairing, coordination polymer hydrogel.

The aqueous equimolar reaction of Ag(i) ions with the thionucleoside enantiomer (-)6-thioguanosine, ((-)6tGH), yields a one-dimensional coordination polymer {Ag(-)tG} n , the self-assembly of which generates left-handed helical chains. The resulting helicity induces an enhanced chiro-optical response compared to the parent ligand. DFT calculations indicate that this enhancement is due to delocalisation of the excited state along the helical chains, with 7 units being required to converge the calculated CD spectra. At concentrations ≥15 mmol l-1 reactions form a sample-spanning hydrogel which shows self-repair capabilities with instantaneous recovery in which the dynamic reversibility of the coordination chains appears to play a role. The resulting gel exhibits circularly polarised luminescence (CPL) with a large dissymmetry factor of -0.07 ± 0.01 at 735 nm, a phenomenon not previously observed for this class of coordination polymer.

Synthesis and surface characterization of new triplex polymer of Ag(I) and mixture nucleosides: cytidine and 8-bromoguanosine.

In this work one-dimensional (1D) triplex polymer of silver (I): mixture nucleosides of cytidine and 8-bromoguanosine was synthesised. The polymer showed high stability due to the presence Ag(I) ions in the structure of the polymer in addition to the stability that produces from the effect of Hoogsteen hydrogen bonding in the triplex CGC. Atomic Force Microscopy (AFM) and transmission electron microscopy (TEM) were used to investigate the morphology of the polymer. The AFM images revealed formation of nanofibres extending many microns in length with height in the range of 2-3 nm. Statistical analyses carried out to analyse the AFM images to determine the height of the loops that formed in the polymer. The data displayed that the height value was in the range between 10 nm to 15 nm. The data of TEM images were consistent with the data of AFM images by displaying a very long fibre. Gwyddion software program was used to investigate surface parameters (roughness and waviness), diameter (size distribution), and probability density of the fibre. The data showed that the diameter of the fibre was ∼0.4 nm.

A coordination polymer for the site-specific integration of semiconducting sequences into DNA-based materials.

Advances in bottom-up material design have been significantly progressed through DNA-based approaches. However, the routine integration of semiconducting properties, particularly long-range electrical conduction, into the basic topological motif of DNA remains challenging. Here, we demonstrate this with a coordination polymer derived from 6-thioguanosine (6-TG-H), a sulfur-containing analog of a natural nucleoside. The complexation reaction with Au(I) ions spontaneously assembles luminescent one-dimensional helical chains, characterized as {AuI(µ-6-TG)} n , extending many µm in length that are structurally analogous to natural DNA. Uniquely, for such a material, this gold-thiolate can be transformed into a wire-like conducting form by oxidative doping. We also show that this self-assembly reaction is compatible with a 6-TG-modified DNA duplex and provides a straightforward method by which to integrate semiconducting sequences, site-specifically, into the framework of DNA materials, transforming their properties in a fundamental and technologically useful manner.Integration of semiconducting properties into the basic topological motif of DNA remains challenging. Here, the authors show a coordination polymer derived from 6-thioguanosine that complexes with Au(I) ions to form a wire-like material that can also integrate semiconducting sequences into the framework of DNA materials.