We report here the synthesis of three novel pi-conjugated heterocyclic mixed trimers that contain two electron-donating 3,4-ethylenedioxy-2-thienyl (EDOT) units covalently attached to a central proquinoid electron-accepting thienopyrazine moiety (two of these narrow-HOMO-LUMO gap D-A-D compounds also bear hexyl side chains attached either to the outermost alpha positions of the EDOT end rings o...

Clusters in Physics The properties of elements from atoms to bulk can be divided into two regimes: (i) a scalable regime where properties vary smoothly as some power law until they reach the bulk limit and (ii) a nonscalable regime where the variation is highly nonmonotonic (1). In this latter region, characterized by clusters, unusual things can and often do arise because of quantum confinemen...

The polarizability and second hyperpolarizability of fulvene, dimethylene-cyclobutene, trimethylene-cyclopropane, bicyclopentadiene-propane, bicyclopentadiene-propene, Dewar benzene, benzvalene and several of their anions are computed, employing a CNDO coupled Hartree-Fock procedure. The interaction of the lone pair on the anionic center with double and single bonds, the HOMO-LUMO gap, and subs...

Two Pt-H vibrational bands at 1679 cm(-1) and 1392 cm(-1) observed with 13-atom Pt clusters supported in LTL zeolite by Fourier Transform Infrared (FTIR) spectroscopy confirms that H atoms bridge two Pt atoms across the edges of the metal cluster. An additional broad absorption band centred near 2200 cm(-1) which exhibits some substructure is assigned to low energy electronic excitations across...

The difference between oxide and hydrogen passivation of small Si nanocrystals is explored by all-electron, hybrid functional DFT calculations with unrestricted geometry optimization. Oxide passivation lowers the band gap by about 2.4 eV for Si35 cores and by about 1.5 eV for Si66 cores. The oxide-passivated nanocrystals have optically forbidden, indirect-gap-type transitions whereas the hydrog...

The research in new organic π-conjugated molecules with specific properties has become one of the most interesting topics in fields of materials chemistry. These materials are promising for optoelectronic device technology such as solar cells. On the other hand, the use of low band gap materials is a viable method for better harvesting of the solar spectrum and increasing its efficiency. The co...

diels–alder [2+4] cycloaddition products of the reaction between c20 and c4h4x2 or c2o2x2 (x = h, f, cl, ch3, nh2, no2, and oh) were studied atb3lyp level of theory with 6-31g, 6-31g(d, p) and 6-311g(d, p) basis sets. the homo–lumo gaps of kohn–sham orbitals for most of the adducts show evident increase compared with the gap value of c20, suggestive of more stability in the adducts. the thermod...

We investigated the electronic properties of N(5)-ethyl flavinium perchlorate (Et-Fl(+)) and compared them to those of its parent compound, 3-methyllumiflavin (Fl). Absorption and fluorescence spectra of Fl and Et-Fl(+) exhibit similar spectral features, but the absorption energy of Et-Fl(+) is substantially lower than that of Fl. We calculated the absorption signatures of Fl and Et-Fl(+) using...

The derivative discontinuity of the exchange-correlation functional of density-functional theory is cast as the difference of two types of electron affinities. We approximately evaluate this difference via ordinary Kohn-Sham calculations, obtaining estimates of the discontinuity for light atoms and for polyacetylene oligomers. The discontinuity is found to be quite large (typically several eV),...