Sterically driven electronic properties of naphthalene- and anthracene- end-capped 2,2'-bipyridine luminophores: synthesis and density functional theory

Two naphthalene- and one anthracene-end-capped 4,4'-Π-conjugated-2,2'-bipyridine chromophores have been synthesized via the Horner-Wordsworth-Emmons reaction protocol and their electronic absorption and emission properties have been examined. DFT and TD-DFT computational studies have been carried out in order to comprehend the role of steric factor over the electronic factor

D-π-A-A-π-D prototype 2,2'-bipyridine dyads exhibiting large structure and environment sensitive fluorescence: synthesis, photophysics and computation

A series of 4,4'-π -conjugated-2,2'-bipyridine chromophores (MS 1-8) were synthesized, and their photophysical and thermal properties were investigated. The title "push-pull' chromophores", except MS 1, were integrated with both alkoxy and alkylamino donor functionalities that differ in their donation capabilities. The oligophenylenevinylene (OPV) chromophores MS 4-8 are associated with a p-extended backbone in which the position and the number of alkoxy donors were systematically varied. All of the studied systems possess a D-π -A-A-π -D dyad archetype in which the A-A is the central 2,2'-bipyridine acceptor core that is electronically attached with the donor termini through p-linkers. The fluorescence quantum yields of the synthesized chromophores are found to be sensitive to the molecular archetype and the solvent medium. Out of the eight fluorescent compounds reported in this article, the compound MS 5 exhibits fluorescence in the solid state also. The modulating effect of the nature, position, and number of donor functionalities on the optical properties of these classes of compounds has further been comprehended on the basis of DFT and TD-DFT computation in a solvent reaction field

Catalytic Enantioselective Syn-Hydroxy-Oxyacylation of Electron Deficient Alkenes

Asymmetric syn-dihydroxylation and dioxyacylation of alkenes have been well established. A direct method for the enantioselective preparation of orthogonally protected syn-1,2-diols from alkenes is unprecedented. Here in, we report the first enantioselective hypervalent iodine catalyzed syn-hydroxy-oxyacylation of enones. The orthogonally protected diols were obtained with excellent diastereo- and regioselectivity under metal-free condition. For these electron-deficient alkenes, even the syn-dihydroxylation and dioxyacylation have remained yet an unfinished challenge

Conformational preferences of mono-substituted cyclohydronitrogens: a theoretical study

The conformational stability of mono-substituted six membered cyclic hydronitrogens (N<SUB>6</SUB>H<SUB>5</SUB>X) are investigated with the aid of electronic structure calculations. One or both hydrogens adjacent to the substituent bearing nitrogen move to the equatorial position to attain the global minimum depending on the electronegativity of X. For example, strongly electronegative substituent like F pushes both the adjacent hydrogens into equatorial position, whereas covalent bond forming amino group prefers both the hydrogens to be in the axial position. When chlorine is the substituent, it migrates to the other end of the ring and forms hydrogen bonds with two of the axial hydrogen atoms in that region. Natural bond orbital analysis indicates that all these phenomena are a manifestation of the anomeric effect to different degrees

D-π-A-A-π-D Prototype 2,2′-Bipyridine Dyads Exhibiting Large Structure and Environment-Sensitive Fluorescence: Synthesis, Photophysics, and Computation

A series of 4,4′-π-conjugated-2,2′-bipyridine chromophores (<b>MS 1</b>–<b>8</b>) were synthesized, and their photophysical and thermal properties were investigated. The title “push–pull’ chromophores”, except <b>MS 1</b>, were integrated with both alkoxy and alkylamino donor functionalities that differ in their donation capabilities. The oligophenylenevinylene (OPV) chromophores <b>MS 4</b>–<b>8</b> are associated with a π-extended backbone in which the position and the number of alkoxy donors were systematically varied. All of the studied systems possess a D-π-A-A-π-D dyad archetype in which the A-A is the central 2,2′-bipyridine acceptor core that is electronically attached with the donor termini through π-linkers. The fluorescence quantum yields of the synthesized chromophores are found to be sensitive to the molecular archetype and the solvent medium. Out of the eight fluorescent compounds reported in this article, the compound <b>MS 5</b> exhibits fluorescence in the solid state also. The modulating effect of the nature, position, and number of donor functionalities on the optical properties of these classes of compounds has further been comprehended on the basis of DFT and TD-DFT computation in a solvent reaction field