Compositions for medicinal Chemistry of fullerenes

The paper presents a quantum-chemical approach to two aspects of fullerene nanomedicine related to the oxidative and antioxidant actions of fullerene. The first topic is concerned in regards photodynamic therapeutic effect of fullerene solutions. A new mechanism of the effect is proposed. The second aspect is exemplified by the consideration of two fullerene-silica complexes, namely, fullerosil and fullerosilica gel.Стаття присвячена квантово-хімічному розгляду двох аспектів наномедицини фулерену, які стосуються його оксидативної та антиоксидативної функцій. Перший аспект розглянуто по відношенню до фотодинамічного терапевтичного ефекту розчинів фулерену. Запропоновано новий механізм цього ефекту. Другий аспект обговорюється на прикладі двох комплексів фулерену з кремнеземом: фулеросилу та фулеросилікагелю.Статья посвящена квантово-химическому рассмотрению двух аспектов наномедицины фуллерена, относящихся к его оксидативной и антиоксидантной функциям. Первый аспект рассмотрен применительно к фотодинамическому терапевтическому эффекту растворов фуллерена. Предложен новый механизм этого эффекта. Второй аспект обсуждается на примере двух комплексов фуллерена с кремнеземом: фуллеросила и фуллеросиликагеля

Virtual Vibrational Spectrometry of Stable Radicals—Necklaced Graphene Molecules

The article presents results of an extended virtual experiment on graphene molecules per-formed using the virtual vibrational spectrometer HF Spectrodyn that exploits semiempirical Har-tree-Fock approximation. The molecules are composed of flat graphene domains surrounded with heteroatom necklaces. Not existing individually, these molecules are met in practice as basic structure units of complex multilevel structure of all sp2 amorphous carbons. This circumstance deprives the solids’ in vitro spectroscopy of revealing the individual character of basic structural elements, and in silico spectrometry fills this shortcoming. The obtained virtual vibrational spectra allow for drawing first conclusions about the specific features of the vibrational dynamics of the necklaced graphene molecules, caused by spatial structure and packing of their graphene domains as well as by chemical composition of the relevant necklaces. As shown, IR absorption spectra of the molecules are strongly necklace dependent, once becoming a distinct spectral signature of the amorphous body origin. Otherwise, Raman spectra are a spectral mark of the graphene domain’s size and pack-ing, thus disclosing the mystery of their universal D-G-band standard related to graphene-contain-ing materials of various origin

Ферромагнетизм в графеновых и фуллереновых наноструктурах. Теория, моделирование, эксперимент

This work is devoted to the construction of the quantum field model, allowing, in particular, to describe ferromagnetic properties in graphen structures adequately to the results of physical and numerical experiments. The offered model describes properties of monoatom graphen layers ( forming two-dimensional surfaces), which are connected with presence of nontrivial function of distribution of the spin density, formed as a result of spontaneous breakdown of the spin symmetry of valent electrons in atoms of carbon. Within the limits of the offered model possible exact solutions for field function of the spin density, explaining, in particular, experimentally observed ferromagnetic properties of graphen films are specified. Quantitative estimations of a thickness of the domain wall, dividing areas with counterdirected vectors of magnetization were suggested, which allows to check up offered theoretical model experimentally.Работа посвящена построению квантовополевой модели, позволяющей, в частности, описывать ферромагнитные свойства в графеновых структурах адекватно имеющимся физическим и численным результатам. Предлагается модель, описывающая такие свойства графеновых моноатомных слоёв, образующих двумерные поверхности, которые связаны с наличием нетривиальной функции распределения спиновой плотности, образованной в результате спонтанного нарушения спиновой симметрии валентных электронов атомов углерода на указанных поверхностях. В рамках предлагаемой модели указываются возможные точные решения для функции спиновой плотности, объясняющие, в частности, экспериментально наблюдаемые ферромагнитные свойства графеновых плёнок. Делаются количественные оценки толщины доменной стенки, разделяющей области с разнонаправленной намагниченностью, позволяющие экспериментально проверить предлагаемую теоретическую модель

Nanophotonics of fullerene. 1. Chemistry and medicine

Discussed in the paper makes it possible to suggest that the formation of positive-negative fullerene ion pair at each photon absorption action is characteristic for photo stimulated events in chemistry and medicine thus providing their common origin. Copyright © 2011 American Scientific Publishers. All rights reserved

Multi-mode ground state interaction terms in C-60-based electron donor-acceptor complexes

Quantum-chemical testing of donor-acceptor properties of binary molecular complexes, related to the singlet state, is suggested as QCh calculations of studied systems and their constituents by using both spin-nondependent (RHF) and spin-dependent ( UHF) versions of the exploited computational tool. The avoided crossing of intermolecular interaction terms of neutral molecules E-int(A(0)B(0)) and molecular ions E-int(A(+)B(-)) causes a multi-mode character of the ground state term. The dependence of D-A complex properties on the type of the term, space positions of the term minimum, and the interrelation of the corresponding energies are discussed. The suggested approach has been applied to binary complexes C-60+X ( X= TAE, TDAE, DMMA, COANP, 2Li, Mg). (C) Central European Science Journals. All rights reserved

Molecular Theory of Graphene

Odd electrons of benzenoid units and the correlation of these electrons having different spins are the main concepts of the molecular theory of graphene. In contrast to the theory of aromaticity, the molecular theory is based on the fact that odd electrons with different spins occupy different places in the space so that the configuration interaction becomes the central point of the theory. Consequently, a multi-determinant presentation of the wave function of the system of weakly interacting odd electrons is utterly mandatory on the way of the theory realization at the computational level. However, the efficacy of the available CI computational techniques is quite restricted in regard to large polyatomic systems, which does not allow performing extensive computational experiments. Facing the problem, computationists have addressed standard single-determinant ones albeit not often being aware of the correctness of the obtained results. The current chapter presents the molecular theory of graphene in terms of single-determinant computational schemes and discloses how reliable information about the electron-correlated system can be obtained by using either UHF or UDFT computational schemes

Odd electrons and covalent bonding in fullerenes

The electronic structure of X60 molecules (X=C, Si) is considered in terms of 60 odd electrons and the spin-dependent interaction between them. The conditions for the electrons to be excluded from the covalent pairing are discussed. A computational spin-polarized quantum-chemical scheme is suggested to evaluate four parameters (energy of radicalization, exchange integral, atom spin density, and squared spin) to characterize the effect quantitatively. A polyradical character of the species, weak for C60 and strong for Si60, is established. © 2004 Wiley Periodicals, Inc

Multi-mode ground state interaction terms in C60-based electron donor-acceptor complexes

Quantum-chemical testing of donor-acceptor properties of binary molecular complexes, related to the singlet state, is suggested as QCh calculations of studied systems and their constituents by using both spin-nondependent (RHF) and spindependent (UHF) versions of the exploited computational tool. The avoided crossing of intermolecular interaction terms of neutral molecules Eint(A0B0) and molecular ions Eint(A+B-) causes a multi-mode character of the ground state term. The dependence of D-A complex properties on the type of the term, space positions of the term minimum, and the interrelation of the corresponding energies are discussed. The suggested approach has been applied to binary complexes C60+X (X= TAE, TDAE, DMMA, COANP, 2Li, Mg). © Central European Science Journals. All rights reserved

Donor-acceptor origin of fullerene C60 dimerization

The fullerene dimerization is considered as a consequence of donor-acceptor interaction between monomer molecules which is significant for C 60+C60 binary system. The dimerization is provided by a two-well structure of the ground state energy term. Analyzing characteristics of the term, proven by quantum-chemical calculations at different starting intermolecular distances, mechanisms of both physically (photoexcitation, thermal, high pressure, plasma, electron beam, and electric field) and chemically (alkali-metal adducts AC60) stimulated dimerization processes are suggested. &copy ;2007 Wiley Periodicals. Inc

Computational synthesis of C 60 cyano- and azopolyderivatives

The cyanation of C 60 to C 60(CN) 18 and the aziridination of C 60 to C 60(NH) 9 were studied by an unrestricted broken spin symmetry Hartree-Fock approach implemented in semiempirical codes based on the AM1 technique. The calculations focused on the successive addition of CN and NH moieties to the fullerene cage following the identification of the target cage atoms as those with the highest atomic chemical susceptibilities calculated at each step. The results obtained were analyzed from the viewpoint of the parallelism between these derivatives as well as C 60 fluorides and hydrides. The difference between the first-stage C 60 chlorination and other sterically free processes is discussed. © Springer-Verlag 2011