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Eight complexes of various aromatic molecules with water have been studied theoretically at the local Møller-Plesset 2nd order theory (LMP2)/aug-ccpVTZ(-f)//LMP2/6-31ϩG* level of theory. Two types of complexes can be formed, depending on the electronic structure of aromatic molecules. Donor hydrocarbons form A-type complexes, while aromatics bearing electron-withdrawing substituents form Btype complexes. A-type complexes are stabilized due to -H interactions with the OH bond pointing to the aromatic molecule plane, while B-type complexes have geometry with the oxygen atom pointing to the aromatic molecule plane stabilized by the interaction of highest occupied molecular orbital (HOMO) of water molecule with * orbitals of the aromatics. It has been found that a (OHOMO-lowest unoccupied molecular orbital (LUMO)/2 value of aromatic molecule, which can be called "molecular electronegativity," is useful to predict the type of complex formed by aromatic molecule and water. Aromatic hydrocarbons with "molecular electronegativity" of Ͻ0.15 tend to form A-type complexes, while aromatic molecules with "molecular electronegativity" of Ͻ0.15 a.u. form B-type complexes. The binding energy of water-aromatic complexes undergoes a minimum in the area of switching from A-type to B type complexes, which can be rationalize in terms of frontier orbital interactions.

Benzene, pyrimidine, and naphthalene dimers have been studied at canonical MP2, LMP2, and MP4(SDTQ) levels of theory. It has been shown that the LMP2 method is superior to canonical MP2 due to reduced BSSE. Thus, basis set limit-extrapolated LMP2 binding energies of T-shaped and parallel displaced (PD) benzene dimers are nearly the same, as has been found in higher level ab initio calculations. MP4(SDTQ) binding energies calculated at LMP2 optimized geometries are always more negative than those calculated for MP2-optimized geometries. MP4(SDTQ)/CC-pVDZ-corrected complete basis set-extrapolated LMP2 binding energies of T-shaped and PD dimers of benzene and naphthalene were found to be -2.80, -2.59 and -4.39, -6.29 kcal/mol, respectively.

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ABSTRACT:A Novel monomer 9,I0-bis(4-hydroxy-1-butynyl)anthracene (Ml) was synthesized and some polyesters and polyurethanes containing a donor 9, 10-diethynylanthracene and acceptor pyromellitic diimide groups were prepared. The polymers were soluble in common organic solvents and gave transparent films by casting. They showed 5% weight loss at the temperature 250-300°C. All polymers showed luminescence and maximum depended on polymer composition. Polymers containing the 9,10-diethynylanthracene moiety alone showed luminescence with maximum at 470-480nm while those containing 9,10-diethynylanthracene and pyromellitic diimide groups showed luminescence with maximum around 600nm due to the charge transfer complex (CTC) formation between them. Some polymers showed electroluminescence with turn-on voltage of 10.5 V.

The ground-state structures of the van der Waals dimers of naphthalene, indole, and 2,3-benzofuran have been optimized at the local MP2/6-31G* level of theory without any symmetry restrictions. The binding energies of complexes were evaluated at the local MP2 approximation using 6-31G*, 6-311G**, cc-pvtz(-f), and aug-pvtz(-f) basis sets. The binding energies are strongly dependent on the basis set size and not completely converged even for the largest basis set tested. The relative stability of studied complexes is, however, similar for the two largest basis sets used in this study. It was found that in all cases the major contribution to the binding energy is the correlation energy representing from 90 to 100% of all stabilization energy. Among two types of studied complexes, parallel and T-shaped, the parallel complexes are the most stable ones due to better correlation stabilization, with one of the naphthalene parallel dimers being the most stable out of all studied complexes showing the stabilization energy of -8.02 kcal/mol. All indole and T-shape 2,3-benzofuran dimers evidence N-H and C-H-π hydrogen bonds as follows from the geometry changes and the charge transfer from one molecule to another. The Kitaura-Morokuma analysis of SCF binding energy shows that T-shape complexes are better stabilized by electrostatic interactions and less destabilized by exchange repulsion compared to parallel ones.

ABSTRACT:The complex formation between fullerene C60 and simple donor molecules such as dimethyl ether, dimethylamine, dimethylsulfide, furan, pyrrole, and thiophene has been studied applying the hybrid MP2/6-31G(dЈ):PM3 ONIOM approach for geometry optimization. Local implementation of Møller-Plesset perturbation theory in combination with 6-31G(d) and 6-311G(d,p) basis sets was used for binding energies estimation of fullerene complexes. Two factors were found to contribute most to the complex stability: the polarizability and molecular volume of donor molecule. As follows from positive stabilization energies at the Hartree-Fock level, the stabilization of fullerene complexes is entirely due to dispersion interactions in accordance with available experimental data. The calculations show that for donors of similar molecular volume the binding energy of molecular complex increases with polarizability of donor molecules. Similarly, for such complexes the partial charges on molecules increase with decreasing of ionization potentials of donor molecules.