Internal Conversion with 3,5-Dimethyl-4-(methylamino)benzonitrile in Alkane Solvents
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I. Rückert
With 3,5-dimethyl-4-(methylamino)benzonitrile (MHD) in n-hexane and n-hexadecane at 25°C, relatively small values are obtained for the fluorescence quantum yield Φf (0.006) and the lifetime τ (0.103 ns). From Φf and the yield of intersystem crossing ΦISC (0.024), it follows that MHD in these solvents undergoes efficient internal conversion with a yield ΦIC of 0.96 and an IC rate constant kIC of 9×109 s-1. An IC activation energy of 12 kJ/mol is obtained from the measurement of τ as a function of temperature in n-hexane. The amino group of MHD in the electronic ground state S0 is twisted relative to the benzonitrile moiety, as deduced from quantum chemical calculations supported by experiments. It is assumed that the IC reaction is a consequence of the planarisation of the amino group upon excitation to the relaxed S1 state and passes through a conical intersection. In support of this mechanism, efficient IC is not observed with the planar derivative 4-amino-3,5-dimethylbenzonitrile (HHD), in contrast to the strongly twisted 3,5-dimethyl-4-(dimethylamino)benzonitrile (MMD).
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- A Thermodynamic Method of Estimating Anharmonic Molecular Densities of States
- The Heterogeneous Kinetics of the Reactions ClONO2 + HX/ice (X = Br, I), BrONO2 + HI/ice and the Reactivity of the Interhalogens BrCl, ICl and IBr with HX/ice (X = Cl, Br, I) in the Temperature Range 180 to 205 K
- Collisional Deactivation of Highly Vibrationally Excited SO2: A Time-Resolved FTIR Emission Spectroscopy Study
- Transitions in Order and Molecularity with Temperature in Gaseous Metal Oxidation Reactions. The Sb-O2 System
- Kinetic Analysis of Complex Chemical Activation and Unimolecular Dissociation Reactions using QRRK Theory and the Modified Strong Collision Approximation
- Chemical Reactions in Ionic Molecular Aggregates. An ab initio and R2PI-Study of the Halogenbenzene/Ammonia System
- Internal Conversion with 3,5-Dimethyl-4-(methylamino)benzonitrile in Alkane Solvents
Articles in the same Issue
- Approximate Factorization of Molecular Potential Surfaces II. Internal Rotors
- A Thermodynamic Method of Estimating Anharmonic Molecular Densities of States
- The Heterogeneous Kinetics of the Reactions ClONO2 + HX/ice (X = Br, I), BrONO2 + HI/ice and the Reactivity of the Interhalogens BrCl, ICl and IBr with HX/ice (X = Cl, Br, I) in the Temperature Range 180 to 205 K
- Collisional Deactivation of Highly Vibrationally Excited SO2: A Time-Resolved FTIR Emission Spectroscopy Study
- Transitions in Order and Molecularity with Temperature in Gaseous Metal Oxidation Reactions. The Sb-O2 System
- Kinetic Analysis of Complex Chemical Activation and Unimolecular Dissociation Reactions using QRRK Theory and the Modified Strong Collision Approximation
- Chemical Reactions in Ionic Molecular Aggregates. An ab initio and R2PI-Study of the Halogenbenzene/Ammonia System
- Internal Conversion with 3,5-Dimethyl-4-(methylamino)benzonitrile in Alkane Solvents
