Synthesis,structure and properties of perimidine spirans

A study was carried out on a new class of photo- and thermochromic spirocyclic cyclohexadienoneperimidines and 4H-naphtholinoneperimidines. The structures of two of these compounds were determined. The lengths of the C_spiro-N bonds were found to be unequivalent; one of these bonds is cleaved in the photo- and thermochromic transformations. The nitrogen atom of the perimidine ring in both compounds was found to have pyramidal configuration with cis arrangement of the unshared electron pairs, while the cyclohexadienone fragments are strongly distorted toward the boat conformation. The nature of the dependence of the photo- and thermochromic properties on their structure and solvent was established.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 702–708, March, 1991.     

Synthesis of perimidine and fused perimidine derivatives from reaction of 1,8-naphthalenediamine with an iminoisocoumarin

The isocoumarin derivative 1H-1-acetylimino-3-methylbenzo[c]pyran-4-carbonitrile reacts with 1,8-naphthalenediamine under basic conditions to give, primarily, 12-acetylisoquino[2,1-a]perimidin-13-amine. This undergoes a variety of reactions to give other isoquino[2,1-a]perimidine derivatives, ring opening to 2-(1H-perimidin-2-yl)phenylacetic acid derivatives and, in polyphosphoric acid, a new hexacyclic system, 6-methyl-7,13,13d-triazadibenzo[def,qr]chrysene.     

Photoelectron spectroscopic investigation of perimidine derivatives

The Hel UPS spectra of acetamidine, perimidine, and four 2-substituted perimidine derivatives have been recorded and interpreted using ab initio and MNDO quantum-chemical calculations. A large interaction between the naphthalene and amidine fragment was concluded from the lowest ionization energy. The color-determining band of these compounds is strongly affected by the intramolecular charge-transfer transitions, which are of low energy because of the low ionization energy of the perimidine moiety.     

Structure and properties of perimidine and its derivatives

The electronic absorption spectra, luminescence spectra, and vibrational spectra of perimidine and its derivatives have been studied. On the basis of the dipole moments and vibrational spectra, the conformations of 2-(o-hydroxyphenyl)perimidine and 2-(o-hydroxyphenyl)perimidine and 2-(o-methoxyphenyl)perimidine, which are stabilized by intramolecular hydrogen bonds, have been established. The electronic configurations of the perimidines in the ground and first excited states have been calculated by Hückel's MO method. The results have been compared with data on the reactivity and electronic absorption spectra of the perimidines.     

Electronic structure of francium

This article presents the first calculations of the electronic structure of francium for the bcc, fcc, and hcp structures, using the linearized augmented plane wave (LAPW) method. Both the local density approximation (LDA) and generalized gradient approximation (GGA) were used to calculate the electronic structure and total energy of francium (Fr). The GGA and LDA both found the total energy of the hcp structure to be slightly below that of the fcc and bcc structures, respectively. This is in agreement with similar results for the other alkali metals where the bcc structure is found not to be the ground state in contradiction to experiment. The equilibrium lattice constant, bulk modulus, and superconductivity parameters were calculated. Calculations of the enthalpy of the system suggest a structural transition from hcp to bcc under a pressure of 0.57 GPa. Using the McMillan‐Gaspari‐Gyorffy theories, we found that under further pressures, in the range of 3–14 GPa, Fr could be a superconductor with critical temperature up to 7 K. This is consistent with the other alkali metals and originates from an increase of the d‐like density of states at the Fermi level, which makes the alkali metals behave like transition metals. © 2013 Wiley Periodicals, Inc.     

Electronic structure of phthalocyanines

Dependence of the energy levels, electron density, position of the absorption bands, singlet-triplet separation, and transition dipole moments of phthalocyanines on the acceptor properties of the central ion, and substitution of the hydrogen atoms by chlorine atoms have been investigated. The nature of the induction effect is considered. Results are compared with the experimental values.     

Electronic structure of dioxazines

The electronic spectra of dioxazines are interpreted by means of the semiempirical Pariser-Parr-Pople method.     

Electronic structure of adamantane

The geometry and electronic structure of adamantane and related molecular cations is studied with the emphasis on the electron density distribution on the face planes and in the carbon cage. The results are compared with the corresponding data for the boron hydrides and carbocations. The bonding in these compounds is discussed in terms of the theory of trishomoaromacity. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Electronic structure of beryllium

The electronic energy bands in beryllium have been recalculated. The earlier work of Terrell [1] was found to contain a systematic error in the form of overlapping muffin tins. The new band structures give a density of states with the Fermi surface lying in the hole like portion, consistent with Hall measurements. All existing calculations misplaced the Fermi surface. As a further check on the new bands, the Hall coefficient A_H was calculated. We obtained A_H = (7.6 ± 0.8) × 10^?24 cgs units for the easy axis or c direction, in excellent agreement with the experimental value of A_H = 8.56 × 10²⁴ cgs units.     

Electronic structure of xDNA

xDNA is an artificial duplex made of natural and benzo-homologated bases. The latter can be seen as a fusion between benzene and a natural base. We have used two different ab initio techniques, one based on B3LYP and a Gaussian expansion of the wave functions, and the other on GGA and plane-waves, to investigate the electronic properties of an xDNA duplex and a natural one with an analogous sequence. The calculations were performed in dry conditions, i.e., H atoms were used to neutralize the charge. It is found that the HOMO-LUMO gap of xDNA is about 0.5 eV smaller than that of B-DNA, independent of the technique used. The pi-pi* gap of xDNA is 1.3 or 1.0 eV smaller than that of B-DNA, depending on whether one uses B3LYP/6-31G or GGA/plane-waves, respectively. An analysis of how saturation changes the electronic properties of the nucleotide pairs that make up these duplexes suggests that different saturation schemes significantly affect the HOMO-LUMO gap value of xDNA and B-DNA. The same is not true for the pi-pi* gap. That xDNA has a smaller pi-pi* gap than B-DNA suggests that xDNA could be a plausible candidate for molecular-wire applications.