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The fundamental issue of conceptually assessment of the total pi-electronic energy is here addressed towards the possibility in assuming the electronegativity and chemical hardness within a quantum parabolic energetic effect that closely resembles other pi-equivalent energy expressions within the semi-empirical computation framework as better as the carbon-based system increases its complexity. On...
Polymers can be cooled down to ultralow temperatures by embedding them in a gas whose temperature is lowered by laser and evaporation cooling. In this regime their fluctuations show quantum behavior. This is calculated here for the second and fourth moments of the end-to-end distribution in the large stiffness expansion. The result should soon be measurable.
Rearrangements of the graphene layers under iterated Stone-Wales rotations are studied here from a pure topological point of view. The analysis provides indications about the relative chemical stability of different isomeric distributions of pentagon–heptagon pairs, the 5|7 structural defects, diffusing in the graphene layer. Our computations are performed in the dual topological space, the Wiener...
We report here a review of our recent efforts at understanding and predicting reactivity and regioselectivity of endohedral (metallo)fullerenes and their parent free fullerenes. The effect of encapsulation of trimetallic nitrides or noble gas atoms/dimers was shown to have a profound impact on the stability and reactivity of fullerene compounds. It is not just the encapsulation, but in particular...
In a previous report, the approximate crystalline structure and electronic structure of a novel, hypothetical hexagonal carbon allotrope has been disclosed. Employing the approximate extended Hückel method, this C structure was determined to be a semi-conducting structure. In contrast, a state-of-the-art density functional theory (DFT) optimization reveals the hexagonal structure to be metallic in...
The visualization of graphs describing molecular structures or other atomic arrangements is necessary in theoretical studying or examining nano structures of several atoms. In the present paper we review previous results obtained by drawing graphs with the help various matrices as the adjacency matrix, the Laplacian matrix and the Colin de Verdière matrix. In examples we show their possibilities and...
The full combinatorial search algorithm and the greedy search algorithm have been used on a set of molecular connectivity indices, five experimental parameters and the molar mass to extract the best descriptor for 12 properties of a set of organic solvents. The quality of the descriptions has been compared with a ‘zero-level’ description based on random numbers. The optimal molecular connectivity...
After an introductory brief discussion of the important and much debated concept of aromaticity, we elaborate on a recently proposed scheme for the partition of π-electrons of Kekuléan polycyclic conjugated hydrocarbons to individual rings, so that by summing π-electrons within individual rings of polycyclic conjugated hydrocarbons one obtains the total number of π-electrons in a molecule. We discuss...
The coding and ordering of benzenoids and their Kekulé structures is discussed. The Wiswesser coding and the binary boundary coding systems are delineated and illustrated. The Wiswesser codes are also used to order cata- and peri-condensed benzenoids. The concept of numeric Kekulé structure is used for coding and ordering Kekulé structures of cata-condensed benzenoids. In the case of peri-condensed...
The stereoisogram approach concludes that chirality and RS-stereogenicity are independent concepts and that prochirality and pro-RS-stereogenicity are independent concepts. Accordingly, the conventional approach should be reorganized, where such confused terms as “chirality”, “stereogenicity”, “prochirality”, and “prostereogenicity” should be replaced by newly-defined attributive terms based on the...
Design of hypothetical crystal networks, consisting of most pentagon rings and generically called diamond D5, is presented. It is shown that the seed and repeat-units, as hydrogenated species, show good stability, compared with that of C60 fullerene, as calculated at DFT levels of theory. The topology of the network is described in terms of the net parameters and Omega polynomial.
We have computed the diameters of all fullerene graphs on 20 ≤ n ≤ 120 vertices and of all fullerene graphs with isolated pentagons on 60 ≤ n ≤ 146 vertices. The results are used to asses the quality of recently obtained linear upper bounds and square root-type lower bounds. It seems that the fullerenes with large diameters are exceedingly rare. Our results suggest that there is a linear upper bound...
In this work we have basically launched a search whether there is a physical process of hardness equalization for molecules similar to the electronegativity equalization. We are tempted by the fact that the electronegativity equalization principle is widely accepted and theoretically justified and there is much communality in the basic philosophy of the origin and operational mechanism of the two...
We have suggested a model for the evaluation of proton affinity of molecules in terms of so\me akin quantum mechanical descriptors that follow closely the physico-chemical process of protonation. Method relies upon the basic tenets of scientific modeling having four akin descriptors – the ionization energy (I), the global softness(S), the electronegativity (χ), and the global electrophilicity index...
Shape is a very important molecular feature for describing ligand molecules interacting with receptor, and other various complex chemical and biological processes. During the last years, there is a strong interest in developing several molecular shape descriptors. In this chapter we present our attempts for deriving van der Waals (vdW) shape molecular descriptors from two size molecular descriptors...
The development of effective nanodelivery systems capable of carrying a drug specifically and safely to a desired site of action can be considered as one of the most challenging tasks of pharmaceutical formulation. Stimuli-responsive materials, as called intelligent or smart, could be the key of the best developments in the area. Controlled Drug Delivery Systems (CDDSs) have almost three decades since...
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