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The intramolecular magnetic couplingconstant (J) values of sets of diradicals linkedto bis-DTDA, OVER, and NN radicals(DTDA, OVER, and NN groups) through an aromatic coupler were studiedby unrestricted density functional theory calculations (UB3LYP/6-311++G(d,p)).Among 15 aromatic couplers, 9 compounds with an odd number of carbonatoms along its spin coupling path were found to interact ferromagneticallyupon coupling with bisradicals while the other 6 couplers with aneven number of carbon atoms along its spin coupling path give riseto antiferromagnetic coupling. The overall trends in the strengthof magnetic interactions of aromatic couplers were preserved for DTDA,OVER, and NN groups so that the trend can be utilized as an indexfor the magnetic strength of a given coupler. It was found that thedifferences in the nucleus-independent chemical shift (NICS), bondorder of connecting bonds, and Mulliken atomic spin density at connectedatoms between triplet and BS states are closely related to the intramolecularmagnetic behavior. 2,4- and 2,5-phosphole couplers exhibit the strongestintramolecular ferromagnetic and antiferromagnetic interactions among15 aromatic couplers when linked to diverse bisradicals. [ABSTRACT FROM AUTHOR]

Detailsof the reaction mechanism for the Ru–PNN pincer complex catalyzedamidation from an alcohol and an amine proposed by Milstein et al.was elucidated using M06 density functional theory calculations. Inaddition, the bifunctional double hydrogen transfer (BDHT) mechanismfor the dehydrogenative oxidation step was investigated for comparison.Finally, the BDHT mechanism was found to be preferred over the β-Helimination pathway that was proposed by Milstein et al. On the basisof the analysis of NBO charges and orbital interactions of intermediatesand transition states, we designed a new catalyst with the additionof an electron-donating substituent (−NEt2), whichprovided much reduced energy barriers and a lower potential energysurface along both mechanisms. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were performed using a MPWB1K functional to interpret the charge transport (CT) properties of stacked annelated β-trithiophene molecules. The goal was to help understand how the chemical composition, face-to-face stacking, intra- and intermolecular correlations, and the applied electric field affect the CT properties of this organic semiconductor compared with those of the edge-to-face "herringbone" motif. The variations in the frontier molecular orbitals, energy gap, nonadiabatic electron attachment energies (EAE), and vertical detachment energies (VDE) were investigated under an external electric field as a function of the number of stacked layers (n). Two possible CT pathways, monomer-to-monomer (MM) and dimer-to-dimer (DD) transports, were postulated to determine the charge carrier conductivities of these molecules. The results highlight that the intermolecular electronic couplings and electrostatic interactions can significantly affect the stacking geometry, even in more extended structures; displaced stacks with smaller interlayer spacing resulted in more compact stacking and, thus, higher CT efficiency; face-to-face stacking geometries can help to reduce the energy gap and VDE. Despite the fact that common thiophene-based oligomers adopting edge-to-face herringbone motifs exhibited p-type (hole-transporting) characters, the face-to-face stacked models based on annelated β-trithiophenes exhibited remarkably increased n-type (electron-transporting) performances. The electric field in the z-direction produced a small influence on the DD charge transport, whereas both electron and hole mobilities decreased dramatically in the MM case. More importantly, in MM charge transport, the electric field increases the hole mobility so that it is higher than that of the electron. [ABSTRACT FROM AUTHOR]

Ithas recently been shown that the types of intramolecular magneticinteractions of diradical systems can be changed by the types of radicalgroup: syn-group (or α-group) and anti-group (or β-group).The aim of this study is to establish a useful scheme to understandand explain the intramolecular magnetic interactions in diradicalsystems regardless of radical groups and the topology of a coupler.We investigated the intramolecular magnetic coupling constant (J) of six oxoverdazyl diradicals (i–vi) coupled with a benzene ring based on the unrestrictedDFT calculations. On the basis of our results, we devised a simplebut useful scheme by combining the spin alternation rule and the conceptof radical group classification. Consequently, it was found that thecalculated Jvalues and plots of spin density distributionswere consistent with our proposed scheme. In addition, we discussed the closed-shell singlet (CS) state and the dihedralangle effect on Jvalues in detail to comprehensivelyunderstand the magnetic interactions of diradical systems. Our schemecan provide the basic framework to design future organic high-spinmolecules and organic magnetic materials. [ABSTRACT FROM AUTHOR]