Synthesis, optical, electrochemical, and computational study of benzene/thiophene based D-π-A chromophores.

We report the design, synthesis, electrochemical, UV-vis, fluorescence, and computational study of nine π-linked donor-acceptor (D-π-A) chromophores. The series of novel compounds comprises a terphenyl, terthiophene, or 2,5-diphenyl thiophene linker, with one electron-donating group (methyl or ,-diethyl) and one electron-withdrawing group (nitrone, formyl, or dicyanovinyl) at opposite ends of the molecule. The HOMO-LUMO gaps were determined cyclic voltammetry and found to correspond well to DFT-calculated values.

Unexpectedly Regioselective Diels-Alder Reactions of New Unsymmetrical Benzoquinones: A Convenient Synthetic Entry to Uniquely Substituted Decalins.

We report flexible synthesis of new unsymmetrically 2,6-disubstituted benzoquinones (33 examples) and a systematic study of their reactivity in the Diels-Alder reaction. The Diels-Alder reactions of selected unsymmetrical benzoquinones with seemingly similar substituents were found to proceed with high regioselectivity and the formation of selected experimentally observed main products was rationalized by theoretical (DFT) calculations. The findings can be exploited in the convenient preparation of densely substituted and stereochemically defined decalins with unique angular substituents at ring fusion.

Mechanisms of Ligand Hyperfine Coupling in Transition-Metal Complexes: σ and π Transmission Pathways.

Theoretical interpretation of hyperfine interactions was pioneered in the 1950s-1960s by the seminal works of McConnell, Karplus, and others for organic radicals and by Watson and Freeman for transition-metal (TM) complexes. In this work, we investigate a series of octahedral Ru(III) complexes with aromatic ligands to understand the mechanism of transmission of the spin density from the d-orbital of the metal to the s-orbitals of the ligand atoms. Spin densities and spin populations underlying ligand hyperfine couplings are analyzed in terms of π-conjugative or σ-hyperconjugative delocalization vs spin polarization based on symmetry considerations and restricted open-shell vs unrestricted wave function analysis.

Mechanistic Analysis of Alkyne Haloboration: A DFT, MP2, and DLPNO-CCSD(T) Study.

Stereocontrol of the alkyne haloboration reaction has received attention in many experimental but few theoretical studies. Here we present a detailed quantum-chemical study of mechanisms leading to versus isomers of haloboration products, considering acetylene and propyne combined with BCl, BBr, and BI. Calculations using B3LYP-D3, MP2, and DLPNO-CCSD(T) methods are used to study polar reactions between the alkyne and BX in the absence and presence of an additional halide anion whose content in the reaction mixture can be controlled experimentally.

Multilayered Polyurethane/Poly(vinyl alcohol) Nanofibrous Mats for Local Topotecan Delivery as a Potential Retinoblastoma Treatment.

Local chemotherapy using polymer drug delivery systems has the potential to treat some cancers, including intraocular retinoblastoma, which is difficult to treat with systemically delivered drugs. Well-designed carriers can provide the required drug concentration at the target site over a prolonged time, reduce the overall drug dose needed, and suppress severe side effects. Herein, nanofibrous carriers of the anticancer agent topotecan (TPT) with a multilayered structure composed of a TPT-loaded inner layer of poly(vinyl alcohol) (PVA) and outer covering layers of polyurethane (PUR) are proposed.