Assignment of the 6,6′-Dioxo-3,3′-biverdazyl Ground State by Using Broken Symmetry and Spectroscopy Oriented Configuration Interaction Techniques

Theoretical investigations on forward-backward ESIPT processes of three fluorophores deriving from 2-(2'-hydroxyphenyl)thiazole

The photophysical properties and excited-state intramolecular proton transfer (ESIPT) processes for 2-(2'-hydroxyphenyl)-4-chloromethylthiazole (1), 2-(2'-hydroxyphenyl)-4-phenylthiazole (2), 2-(2'-hydroxyphenyl)-4-hydroxymethyl-thiazole (3) were studied at the TD-B3PW91/6-31 + G(d, p)/IEFPCM level. The structures of 1-3 were fully optimized and the corresponding structural parameters, infrared spectra and electron densities in the ground (S₀) and the first excited (S₁) states were analyzed. The calculated absorption and fluorescence wavelengths of 1-3 reproduced the experimental data. The potential energy curves of the S₀ and S₁ states were built and the ESIPT processes were clarified. Our results showed that the intramolecular H-bonds of 3 and 2 in the S₁ state were the strongest and the weakest, respectively, and then the ESIPT potential barriers of 3 and 2 were the lowest and highest, respectively. Among the three phenol-thiazole type probes, the compound 2 with phenyl ring group at the 4 position of the thiazole ring had the larger π-conjugation, and had the higher ESIPT potential barrier at the same time. The corresponding compound 1 and 3 with CH₂Cl and CH₂OH had the lower ESIPT barrier.

Performance and multi-scale investigation on the phase miscibility of poly(lactic acid)/amided silica nanocomposites

In this work, amino-functionalized nano-SiO₂ (m@g-SiO₂) was synthesized through coupling reaction on the surface of nano-SiO₂. Moreover, the optimum preparation conditions of m@g-SiO₂ were selected via orthogonal experiments as follows: reaction temperature of 80 °C, reaction time of 8 h, the mass ratio of stearic acid, N,N'‑carbonyldiimidazole, imidazole hydrochloride and g-SiO₂ of 0.5:0.7:0.7:1. Fourier transform infrared spectroscopy, static angle measurement and X-ray photoelectron spectroscopy unanimously confirmed the formation of m@g-SiO₂. Furthermore, poly(lactic acid)(PLA)/m@g-SiO₂ nanocomposites was prepared with m@g-SiO₂ as fillers to improve the comprehensive performance of PLA. Then, the mechanical properties and crystallization behavior of PLA/m@g-SiO₂ nanocomposites were studied, which showed that the impact strength and elongation-at-break of PLA/m@g-SiO₂ (0.3 wt%) nanocomposites were increased by 78.05% and 1148%, respectively, and its crystallinity was increased by 26.46%. Simultaneously, thermal gravimetric analysis indicated that the thermal stability of PLA/m@g-SiO₂ nanocomposites was improved. Eventually, the multi-scale investigation on the phase miscibility of PLA/m@g-SiO₂ nanocomposites was probed by rheological behaviors analysis and the molecular dynamics simulations, which confirmed that surface modification of SiO₂ greatly enhanced the interaction energy and miscibility between the filler and PLA bulk.

Calculation of the 4,5-dihydro-1,3,2-dithiazolyl radical g tensor components by the coupled-perturbed Kohn-Sham hybrid density functional and configuration interaction methods: a comparative study

The g tensor components of the 4,5-dihydro-1,3,2-dithiazolyl (H2DTA•) radical, which is a basic building block for molecular magnets and spintronic devices, is calculated by the coupled-perturbed Kohn-Sham (CPKS) hybrid density functional (HDF) and multireference configuration interaction-sum over states (MRCI-SOS) techniques. In both methods, the diagonalized g tensor principal axes are found to be aligned with the radical's inertial axes. The tensor components are in very good agreement with those determined experimentally by electron paramagnetic resonance (EPR) spectroscopy. The MRCI technique produced g tensor components that are more accurate than those obtained by the CPKS-HDF method. Nonetheless, to get reasonable MRCI results, one must include the in-plane and out-of-plane interactions in an unbiased way. The minimum reference space that satisfies these conditions is generated from a complete active space of nine electrons in six orbitals [CAS(9,6)] and contains a(1), a(2), b(1) and b(2) type orbitals. In addition, the number of roots in the MRCI-SOS g tensor expansion should include all excited states that range from 0 to 56,000 cm(-1). The most accurate results are obtained using an MRCI-SOS/CAS(13,9) calculation. These g tensor components are within the experimental accuracy range of 1000 ppm. The one- and two-electron contributions to the g tensor components are separated and individually analyzed. The very good agreement with experiment opens the door for further accurate calculations of spin Hamiltonian tensors of larger DTA• radicals.