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Li Q.,Key Laboratory of Cluster Science | Blancafort L.,Institute Of Quimica Computacional I Catalisi
Chemical Communications | Year: 2013

A conical intersection seam is behind the restriction of intramolecular rotation mechanism for aggregation induced emission in diphenyl dibenzofulvene (DPDBF). In solution, the seam is accessed through rotation around the exocyclic fulvene bond, leading to radiationless decay to the ground state. In the solid, the seam cannot be accessed because the torsion is blocked, and DPDBF becomes emissive. © 2013 The Royal Society of Chemistry. Source

Vummaleti S.V.C.,King Abdullah University of Science and Technology | Falivene L.,University of Salerno | Poater A.,Institute Of Quimica Computacional I Catalisi | Cavallo L.,King Abdullah University of Science and Technology
ACS Catalysis | Year: 2014

We demonstrate that the experimentally observed switch in selectivity from 5-exo-dig to 6-endo-dig cyclization of an alkynyl substrate, promoted by Au I and AuIII complexes, is connected to a switch from thermodynamic to kinetic reaction control. The AuIII center pushes alkyne coordination toward a single Au-C(alkyne) σ-bond, conferring carbocationic character (and reactivity) to the distal alkyne C atom. © 2014 American Chemical Society. Source

Gomez-Suarez A.,University of St. Andrews | Gasperini D.,University of St. Andrews | Vummaleti S.V.C.,King Abdullah University of Science and Technology | Poater A.,Institute Of Quimica Computacional I Catalisi | And 3 more authors.
ACS Catalysis | Year: 2014

We report a new catalytic protocol for the synthesis of γ,δ-unsaturated carbonyl units from simple starting materials, allylic alcohols and alkynes, via a hydroxalkoxylation/Claisen rearrangement sequence. This new process is more efficient (higher TON and TOF) and more eco-friendly (increased mass efficiency) than the previous state-of-the-art technique. In addition, this method tolerates both terminal and internal alkynes. Moreover, computational studies have been carried out in order to shed light on how the Claisen rearrangement is initiated. © 2014 American Chemical Society. Source

Chakraborty P.,University of Calcutta | Adhikary J.,University of Calcutta | Samanta S.,Presidency University of India | Escudero D.,Max-Planck-Institut fur Kohlenforschung | And 8 more authors.
Crystal Growth and Design | Year: 2014

By using two potential tridentate ligands, HL1 [4-chloro-2-[(2-morpholin-4-yl-ethylimino)-methyl]-phenol] and HL2 [4-chloro-2-[(3-morpholin-4-yl-propylimino)-methyl]-phenol], which differ by one methylene group in the alkyl chain, four new ZnII complexes, namely, [Zn(L2H)2](ClO4)2 (1), [Zn(L 1)(H2O)2][Zn(L1)(SCN)2] (2), [Zn(L1)(dca)]n (3), and [Zn2(L 1)2(N3)2(H2O) 2] (4) [where dca = dicyanamide anion] were synthesized and structurally characterized. The results indicate that the slight structural difference between the ligands, HL1 and HL2, because of the one methylene group connecting the nitrogen atoms provokes a chemical behavior completely different from what was expected. Any attempt to isolate the Zn(L2) complexes with thiocyanato, dicyanamido, and azide was unsuccessful, and perchlorate complex 1 was always obtained. In contrast, with HL1 we obtained structural diversity on varying the anions, but we failed to isolate the analogous perchlorate complex of HL1. Single-crystal X-ray analyses revealed that the morpholine nitrogen of ligand L2 is protonated and thus does not take part in coordination with ZnII in complex 1. On the other hand, the morpholine nitrogen of L1 is coordinated to ZnII in 2-4. Of these, 2 and 4 are rare examples of a cocrystallized cationic/anionic complex and of a dinuclear complex bridged by a single azide, respectively. Some of these unexpected findings and some interesting noncovalent interactions leading to the formation of dimeric entities in solid-state compound 4 were rationalized by a DFT approach. Photoluminescence properties of the complexes as well as the ligands were investigated in solution at ambient temperature and at 77 K. The very fast photoinduced electron transfer (PET) from the nitrogen lone pair to the conjugated phenolic moiety is responsible for very low quantum yield (Φ) exhibited by the ligands, whereas complexation prevents PET, thus enhancing the Φ in the complexes. The origin of the electronic and photoluminescence properties of the ligands and complexes was assessed in light of theoretical calculations. © 2014 American Chemical Society. Source

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