18259-45-5Relevant articles and documents
EPR, ENDOR and TRIPLE Resonance Characterization of Three Paramagnetic Redox Stages of 5-Methylene-5H-dibenzocycloheptene
Franco, M. Luisa T. M. B.,Lazana, M. Celina R. L. R.
, p. 3273 - 3280 (1994)
Radical anions and radical trianions derived from 5-methylene-5H-dibenzocycloheptene 1, 10-deuterio-5-methylene-5H-dibenzocycloheptene 1d and 5-dideuteriomethylene-5H-dibenzocycloheptene 1d2 by reduction with lithium, sodium, potassium and caesium in ethereal solvents have been studied by EPR, ENDOR and TRIPLE resonance spectroscopy.The spin and charge distribution in 1.(1-) and 1.(3-) are discussed both in terms of HMO-McLachlan and INDO calculations.The energies of the lowest unoccupied molecular orbital (LUMO) and of the next lowest unoccupied molecular orbital (NLUMO) are influenced differently by the strong interaction of the supercharged radical trianion with the counter-cations.A change in the orbital sequence of LUMO and NLUMO was predicted theoretically for the radical trianion relative to that found for the radical anion, in accordance with the experimental results.The radical cations 1.(1+), 1d.(1+) and 1d2.(1+) obtained via oxidation by AlCl3 in dichloromethane solution were also studied by EPR, ENDOR and TRIPLE resonance spectroscopy.The experimental results were also interpreted in terms of HMO-McLachlan and INDO methods.
Conformational analysis of some 5-substituted 5H-dibenzo[a,d]-cycloheptenes
Hjelmencrantz, Anders,Friberg, Annika,Berg, Ulf
, p. 1293 - 1300 (2007/10/03)
Conformations and inversion barriers of 5H-dibenzo[a,d]cycloheptene (1a), 5-amino-5H-dibenzo[a,d]cycloheptene (1b), 5-chloro-5H-dibenzo[a,d]cycloheptene (1e), 5-hydroxy-5H-dibenzo[a,d]cycloheptene (1d), 5-methyl-5H-dibenzo[a,d]cycloheptene (1f), N-benzyl-5H-dibenzo[a,d]cyclohepten-5-imine (2) and N-(5H-dibenzo[a,d]cyclohepten-5-yl)benzylideneamine (1c) have been studied by means of dynamic nuclear magnetic resonance spectroscopy (DNMR) techniques, and comparison of the experimentally derived thermodynamic parameters was made with MM3, PM3 and ab initio calculated results. Attempts to determine the inversion barrier of 3-isopropyl-5H-dibenzo[a,d]cyclohepten-5-one (3) failed.
Excited-State Carbon Acids. Facile Benzylic C-H Bond Heterolysis of Suberene on Photolysis in Aqueous Solution: A Photogenerated Cyclically Conjugated Eight ? Electron Carbanion
Budac, David,Wan, Peter
, p. 887 - 894 (2007/10/02)
The possibility of excited-state carbon acid behavior of the dibenzylic protons of several dibenzannelated systems related to suberene (1) has been investigated in aqueous solution and in several organic solvents.It was found that only suberene (1) displayed observable excited-state carbon acid behavior.Thus photolysis of 1 in D2O-CH3CN solutions resulted in facile exchange of the benzylic protons with deuterium from D2O.Extended photolysis resulted in incorporation of two deuteriums at the benzylic position.Quantum yields for initial deuterium incorporation are in the range 0.02-0.03 for 1 in D2O-CH3CN solutions.Deuterium exchange from the benzylic position with solvent protons was also observed on photolysis of 5,5-dideuterio-5H-dibenzocycloheptene (2), where each deuterium atom was exchanged with solvent H2O in a sequential manner.Fluorescence quenching by water (in CH3CN solution) of the exchanging suberene systems (1 and 2) gave linear Stern-Volmer plots, with kq = (1.68 +/- 0.08) * 1E8 M-1 s-1 for 1 and (0.61 +/- 0.06) * 1E8 M-1 s-1 for 2, which corresponds to an isotope effect for quenching by water, (kH/kD)q = 2.8 +/- 0.4.Fluorescence titration of 1 and 11 as a function of medium acidity gave an estimate of pK(S1) ca. -1 for these carbon acids.This compares to their estimated pK(S0) ca. 31-38.
