Extremal topological indices of some nanostructures.

In this work, general formulas of degree-based and neighborhood degree sum-based topological indices for a 2D lattice of H-Naphtalenic nanotubes and pent-heptagonal nanosheets are determined. As an example, six neighborhood degree sum-based topological indices are computed using the obtained formula. Furthermore, the extremal cases of these nanostructures with a fixed number of blocks are characterized for a given degree-based or neighborhood degree sum-based topological index.

Synthesis, characterisation and thermal studies of ruthenium(II) carbonyl complexes of functionalised tripodal phosphine chalcogen donor ligands, [CH(3)C(CH(2)P(X)Ph(2))(3)], where X=Se, S, O.

The polymeric ruthenium(II) carbonyl complex, [Ru(CO)(2)Cl(2)](n) reacts with 1,1,1-tris-(diphenylphosphinomethyl)ethane trichalcogenide ligands, [CH(3)C(CH(2)P(X)Ph(2))(3)], where X=Se(a), S(b) and O(c) in 1:1 (metal:ligand) molar ratio to afford hexa-coordinated complexes of the type eta(2)-(X,X)-[Ru(CO)(2)Cl(2)P(3)X(3)] (1a-c). The complexes 1a-c exhibit two equally intense nu(CO) bands in the range 1979-2060cm(-1) indicating cis-disposition of the two terminal carbonyl groups. The values of nu(CO) frequencies containing different ligands, in general, follow the order: P(3)O(3)>P(3)S(3)>P(3)Se(3) which may be explained in terms of 'Soft-Hard' (Ru(II)-O) and 'Soft-Soft' (Ru(II)-S/Se) interactions.