The conformational flexibility of the expanded porphyrins allows them to achieve different topologies with distinct aromaticities and nonlinear optical properties (NLOP). For instance, it is possible to switch between Möbius and Hückel topologies applying only small changes in the external conditions or in the structure of the ring. In this work, we evaluate the electronic and vibrational contr...

The crystal structure of o-toluidinium chloranilate and m-toluidinium chloranilate, 2CH3C6H4NH3 · C6O4Cl22−, was determined by single crystal X-ray diffraction at room temperature. It was found that o-toluidinium chloranilate (I) is monoclinic, P21/n (#14), Z = 2, a = 5.2184(14), b = 7.825(2), c = 22.840(5) Å, and β = 92.015(19)◦ , and m-toluidinium chloranilate (II) is monoclinic, P21/c (#14),...

A method to approximate ab initio shielding constants is presented, in which the ab initio density matrix is replaced in the gauge invariant atomic orbital formalism with the density matrix resulting from an effective fragment potential calculation. The resulting first-order density matrix is then iterated to self-consistency. The method is compared with fully ab initio gauge invariant atomic o...

The structural saturation and stability, the energy gap, and the density of states of a series of small, siliconbased clusters have been studied by means of the PM3 and some ab initio ~HF/6-31G* and 6-31111G**, CIS/6-31G* and MP2/6-31G*! calculations. It is shown that in order to maintain a stable nanometric and tetrahedral silicon crystallite and remove the gap states, the saturation atom or s...

The relative stabilities of the nine possible isomers for C80O based on C80(D5d) were investigated via density function theory (DFT) at B3LYP/6-31G(d) level. The most stable geometry of C80O is predicted to be 23,24-C80O, where an annulene-like structure is formed. The stretching vibration frequencies of the C=C bonds in the IR spectrum of C80O compared with those of the C=C bonds in the IR spe...

An investigation of the structure and drug release mechanism of a drug delivery system is proposed on the basis of semi-empirical and ab initio computations in vacuum stage. Cis-aconityl linkage is used to improve the interaction between an anti-cancer agent, doxorubicin, and a glycol chitosan biopolymer. It has been found that the doxorubicin-conjugated glycol chitosan carrier has more stabili...

This paper presents computational evidence for the occurrence of diradical mechanism of self-initiation in thermal polymerization of methyl methacrylate. Two self-initiation mechanisms of interest were explored with first-principles density functional theory calculations. Singlet and triplet potential energy surfaces were constructed. The formation of two Diels-Alder adducts, cis- and trans-dim...

The inequivalence of substitution pair positions of naphthalene ring has been investigated by a theoretical measurement of hydrogen bond strength, aromaticity, and excited state intramolecular proton transfer (ESIPT) reaction as the tools in three substituted naphthalene compounds viz 1-hydroxy-2-naphthaldehyde (HN12), 2-hydroxy-1-naphthaldehyde (HN21), and 2-hydroxy-3-naphthaldehyde (HN23). Th...

AIMS/INTRODUCTION Many patients with diabetes now use 5-, 6- or 8-mm needles for insulin injection. However, it is unclear whether needle length, particularly for shorter needles, affects the pharmacokinetic properties of insulin. MATERIALS AND METHODS This was a three-way, randomized, cross-over, single-center study involving 12 healthy Japanese adult males (age 27.4 ± 4.14 years; weight 64....