Photoelectron spectroscopy of HCCN− and HCNC− reveals the quasilinear triplet carbenes, HCCN and HCNC | Zendy

Mark R. Nimlos | Zendy; Gustavo E. Davico | Zendy; C. Michael Geise | Zendy; Paul G. Wenthold | Zendy; W. C. Lineberger | Zendy; Stephen J. Blanksby | Zendy; Christopher M. Hadad | Zendy; George A. Petersson | Zendy; G. Barney Ellison | Zendy

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Photoelectron spectroscopy of HCCN− and HCNC− reveals the quasilinear triplet carbenes, HCCN and HCNC

Author(s) -

Mark R. Nimlos,

Gustavo E. Davico,

C. Michael Geise,

Paul G. Wenthold,

W. C. Lineberger,

Stephen J. Blanksby,

Christopher M. Hadad,

George A. Petersson,

G. Barney Ellison

Publication year - 2002

Publication title -

the journal of chemical physics

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.071

H-Index - 357

eISSN - 1089-7690

pISSN - 0021-9606

DOI - 10.1063/1.1496473

Subject(s) - excited state , chemistry , singlet state , electron affinity (data page) , x ray photoelectron spectroscopy , ion , deprotonation , ground state , proton affinity , triplet state , spectroscopy , atomic physics , analytical chemistry (journal) , molecule , physics , nuclear magnetic resonance , protonation , organic chemistry , quantum mechanics , chromatography

Negative ion photoelectron spectroscopy has been used to study the HCCN- and HCNC- ions. The electron affinities (EA) of cyanocarbene have been measured to be EA(HCCN (X) over tilde (3)Sigma(-)=2.003+/-0.014 eV and EA(DCCN (X) over tilde (3)Sigma(-))=2.009+/-0.020 eV. Photodetachment of HCCN- to HCCN (X) over tilde (3)Sigma(-) shows a 0.4 eV long vibrational progression in nu(5), the H-CCN bending mode; the HCCN- photoelectron spectra reveal excitations up to 10 quanta in nu(5). The term energies for the excited singlet state are found to be T-0(HCCN (a) over tilde (1)A('))=0.515+/-0.016 eV and T-0(DCCN (a) over tilde (1)A('))=0.518+/-0.027 eV. For the isocyanocarbene, the two lowest states switch and HCNC has a singlet ground state and an excited triplet state. The electron affinities are EA(HCNC (X) over tilde (1)A('))=1.883+/-0.013 eV and EA((X) over tilde (1)A(') DCNC)=1.877+/-0.010 eV. The term energy for the excited triplet state is T-0(HCNC (a) over tilde (3)A("))=0.050+/-0.028 eV and T-0(DCNC (a) over tilde (3)A("))=0.063+/-0.030 eV. Proton transfer kinetics in a flowing afterglow apparatus were used to re-measure the enthalpy of deprotonation of CH3NC to be Delta(acid)H(298)(CH3NC)=383.6+/-0.6 kcal mol(-1). The acidity/EA thermodynamic cycle was used to deduce D-0(H-CHCN)=104+/-2 kcal mol(-1) [Delta(f)H(0)(HCCN)=110+/-4 kcal mol(-1)] and D-0(H-CHNC)=106+/-4 kcal mol(-1) [Delta(f)H(0)(HCNC)=133+/-5 kcal mol(-1)]. (C) 2002 American Institute of Physics

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