Wei-Hua Mu

Large Stokes shift induced by intramolcular charge transfer in N,O-chelated naphthyridine-BF2 complexes.

Novel N,O-chelated naphthyridine-BF(2) complexes with push-pull structures have been synthesized and characterized. Spectral investigations on these complexes reveal that photoinduced intramolecular charge transfer occurs and results in a large Stokes shift, which is further supported by density functional theory based theoretical calculations.

Intense one- and two-photon excited fluorescent bis(BF2) core complex containing a 1,8-naphthyridine derivative.

The first bis(BF(2)) core complex containing a 1,8-naphthyridin derivative (1,2-bis(5,7-dimethyl-1,8-naphthyridin-2-yl)hydrazine) and with yellow-green emission as well as a high quantum yield was synthesized and structurally characterized, and the compound exhibits two-photon absorption and excited fluorescence properties.

Competing Mechanisms, Substituent Effects, and Regioselectivities of Nickel-Catalyzed [2 + 2 + 2] Cycloaddition between Carboryne and Alkynes: A DFT Study.

Competing reaction mechanisms, substituent effects, and regioselectivities of Ni(PPh3)2-catalyzed [2 + 2 + 2] carboryne-alkyne cycloadditions were characterized by density functional theory using the real chemical systems and solvent effects considered. A putative mechanism involving the following steps was characterized: (1) exothermic carboryne-catalyst complexation and nucleophilic attack by the first alkyne; (2) insertion of the second alkyne, the rate-determining step (RDS) in all four reactions studied; (3) isomerization of reactant-bound complexes; and (4) product elimination and catalyst regeneration. The RDS in three reactions is mediated by free energy barriers of 27.2, 31.1, and 36.6 kcal·mol(-1), representative of the corresponding experimental yields of 67, 54, and 33%, respectively. A fourth reaction with 0% experimental yield showed representative RDS free energy barriers of 60.4 kcal·mol(-1), which are difficult to surmount even at 90 °C. Alternative pathways leading to differing isomers were similarly characterized and successfully reproduced experimentally determined product regioselectivities. Kinetic data derived from free energy barriers are in quantitative agreement (< ± 0.75-3.0 kcal·mol(-1)) of the experimental times, affirming the theoretical results as representative of the real chemical transformations. Complementary determinations show the use of truncated models (Ni(PMe3)2, Ni(PH3)2) causes the RDS to vary from step 2 (alkyne insertion) to step 1 (alkyne attack), highlighting the need to employ real chemical systems in modeling these reactions.

Multi-Pathway Consequent Chemoselectivities of CpRuCl(PPh3)2/MeI-Catalysed Norbornadiene Alkyne Cycloadditions

Abstract Chemoselectivities of five experimentally realised CpRuCl(PPh3)2/MeI‐catalysed couplings of 7‐azabenzo‐norbornadienes with selected alkynes were successfully resolved from multiple reaction pathway models. Density functional theory calculations showed the following mechanistic succession to be energetically plausible: (1) CpRuI catalyst activation; (2) formation of crucial metallacyclopentene intermediate; (3) cyclobutene product (P2) elimination (ΔG Rel(RDS)≈11.9–17.6 kcal mol−1). Alternative formation of dihydrobenzoindole products (P1) by isomerisation to azametalla‐cyclohexene followed by subsequent CpRuI release was much less favourable (ΔG Rel(RDS)≈26.5–29.8 kcal mol−1). Emergent stereoselectivities were in close agreement with experimental results for reactions a, b, e. Consequent investigations employing dispersion corrections similarly support the empirical findings of P1 dominating in reactions c and d through P2→P1 product transformations as being probable (ΔG≈25.3–30.1 kcal mol−1).