Determination of the absolute rates of decay of arylcarbenes in various low temperature matrixes by electron spin resonance spectroscopy

Photoelimination of Nitrogen from Diazoalkanes: Involvement of Higher Excited Singlet States in the Carbene Formation

“…Synthesis and photochemistry of 2 have been reported by Eguchi et al Photochemistry of 3 − and a number of alkyl phenyl carbene precursors have been investigated, , but no evidence of anti-Kasha photochemistry or fluorescence from higher excited states has been reported. We also investigated photophysics of 2 and 3 , where 2 showed unexpected fluorescence properties (Figures S1–S5 and Table S2 in the Supporting Information).…”

“…The details on the synthesis of 2 and 3 and the description of photochemical experiments are given in the Supporting Information (SI). Synthesis and photochemistry of 2 has been reported by Eguchi et al 28 Photochemistry of 3 [10][11][12][13][14][15][16][17][18][19][20][21][22][23] and a number of alkyl phenyl carbene precursors has been investigated, 29,30 but no evidence of anti-Kasha photochemistry or fluorescence from higher excited states have been reported. We also investigated photophysics of 2 and 3, where 2 showed unexpected fluorescence properties (Figs S1-S5 and Table S2 in the SI).…”

“…8,9 Previous experimental studies were concerned with larger diazoalkanes, particularly diphenyl derivative 3 due to weaker explosive character and easy excitation. The chemistry of carbene car-3 has been completely unraveled, [10][11][12][13][14][15][16][17][18][19][20][21][22][23] but not much has been learned on the photochemical elimination reaction. From the computational side, an early CASSCF study suggested the pos-sibility of a wavelength dependent CH2 + N2 formation in diazirine, 24 but this possibility was subsequently dismissed.…”

Application of radical cage reactions in studies of microstructures of polymers and composites

“…This structural effect was illustrated by the dependence of the initial decay rate of diphenylcarbenes (DPC) in propanol at 77 K on the duration of their photoregeneration from diphenyldiazomethane (DDM). 50,51 The results reported by Bauschlicher et al 52 can be used for the theoretical substantiation of the decisive effect of carbene distribution over spatially oriented parameters on their kinetic non-equivalence in the insertion into the C7H bonds of the solid matrix. These authors calculated the ideal geometric configuration of the classical transition state, which corresponds to the minimum height of the potential barrier of the reaction of triplet methylene with a hydrogen molecule and methane.…”

SOMO–HOMO Conversion in Triplet Carbenes

“…Thus, the two electrons preferably occupy the more delocalized HOMO than the relatively localized SOMO−1 to avoid electronic repulsion. Surprisingly, a simple carbene, fluorenylidene (F), 29,30 in C 2v symmetry with a small carbene angle of 112.0°also exhibited the SOMO−HOMO energy conversion phenomenon at the UB3LYP/6-31G(d) level of theory (Figure 5a). The energetic preference of the triplet state over the closed-shell and openshell singlets was computed to be 6.6 and 3.4 kcal mol −1 , respectively.…”