Biomedical subjects

Elambalassery G Jayasree

Publications and source records attributed to Elambalassery G Jayasree.

3 recordsLinked to original sources

PubMed2005

Hypercarbons in polyhedral structures.

Though carbon is mostly tetravalent and tetracoordinated, there are several examples where the coordination number exceeds four. Structural varieties that exhibit hypercarbons in polyhedral structures such as polyhedral carboranes, sandwich complexes, encapsulated polyhedral structures and novel planar aromatic systems with atoms embedded in the middle are reviewed here. The structural variety anticipated with hypercoordinate carbon among carboranes is large as there are many modes of condensation that could lead to large number of new patterns. The relative stabilities of positional isomers of polyhedral carboranes, sandwich structures, and endohedral carboranes are briefly described. The mno rule accounts for the variety of structural patterns. Wheel-shaped and planar hypercoordinated molecules are recent theoretical developments in this area.

Boron↗

PubMed2003

The rearrangement of dicarboranyl methyl cation: a possible synthetic strategy toward cationic closo-tricarbaboranes.

A quantitative study on cationic closo-tricarbaboranes proved their stability and a possible use for them as weakly coordinating ions due to the dispersal of positive charge throughout the cage. The current study explores computationally a synthetic strategy toward their realization in parallel with the benzyl cation-tropylium ion rearrangement. This study shows that cage expansion along with the incorporation of a carbon atom into the cage starting from the dicarboranyl methyl cation is in the realm of the possible. The rearrangements are found to have favorable energy barriers with one transition state. The geometry of the dicarboranyl methyl cations (benzyl cation analogues) with bent CH(2) groups favors the rearrangement into the tropylium analogues. Thus, the comparison of well-known benzyl ion-tropylium ion rearrangement with similar reactions among polyhedral boranes unravels the feasibility of cationic tricarboranes.

Journal Article↗

PubMed2003

Analogies between boron and carbon.

The structural connections between the compounds of boron and carbon are extended using the mno rule beyond the borane-carbocation continuum, the lithium boride-polycarbyne analogy, and the magnesium boride (MgB(2))-graphite equivalence to beta-rhombohedral boron and fullerenes. The structural similarity of the pentagonal pyramidal C(6)H(6)(2+) and MgB(4) is established. An interesting electronic structural relationship between the B(84) fragment of the beta-rhombohedral boron and the fulleride anion, C(60)(12-), is derived by replacing the 12 pentagonal pyramidal B(6)(4-) units by isoelectronic C(5)(-) units and removing the central B(12) from the electron-deficient B(84) unit. This relationship is well supported by the experimental realization of C(60)M(12) (M = Li, K) and C(48)N(12).

Journal Article↗