Photochemistry of Fumaronitrile Radical Anion and Its Clusters

Abstract

The photodetachment and photochemistry of the radical anion of fumaronitrile (trans-1,2-dicyanoethylene) and its clusters are investigated using photoelectron imaging and photofragment spectroscopy. We report the first direct spectroscopic determination of the adiabatic electron affinity (EA) of fumaronitrile (fn) in the gas phase, EA = 1.21 ± 0.02 eV. This is significantly smaller than one-half the EA of tetracyanoethylene (TCNE). The singlet-triplet splitting in fumaronitrile is determined to be ΔES-T ≤ 2.6 eV, consistent with the known properties. An autodetachment transition is observed at 392 and 355 nm and assigned to the (2)Bu anionic resonance in the vicinity of 3.3 eV. The results are in good agreement with the predictions of the CCSD(T) and EOM-XX-CCSD(dT) (XX = IP, EE) calculations. The H2O and Ar solvation energies of fn(-) are found to be similar to the corresponding values for the anion of TCNE. In contrast, a very large (0.94 eV) photodetachment band shift, relative to fn(-), is observed for (fn)2(-). In addition, while the photofragmentation of fn(-), fn(-)·Ar, and fn(-)(H2O)1,2 yielded only the CN(-) fragment ions, the dominant anionic photofragment of (fn)2(-) is the fn(-) monomer anion. The band shift, exceeding the combined effect of two water molecules, and the fragmentation pattern, inconsistent with an intact fn(-) chromophore, rule out an electrostatically solvated fn(-)·fn structure of (fn)2(-) and favor a covalently bound dimer anion. A C2 symmetry (fn)2(-) structure, involving a covalent bond between the two fn moieties, is proposed.

Barrierless Single‐Electron‐Induced cis–trans Isomerization

“…Unfortunately, a more quantitative evaluation of the lifetime of Feshbach resonances for a molecule of this size is still not possible. We note that recent photodetachment experiments have provided evidence for the existence of an electronic resonance in the FN − anion 16…”

Effective D-A-D type chromophore of fumaronitrile-core and terminal alkylated bithiophene for solution-processed small molecule organic solar cells

“…Due to spontaneous phase-segregation process in the blended active layers of RCNR and PC 60 BM, a bicontinuous network structure might form which creates the percolation channels for the efficient charge carrier collection within the active layer of BHJ solar cells50. On the other hand, the improvement in the V OC value might be due to the presence of two –CN groups which induce the better film morphology and strong intermolecular charge-transfer (ICT) between RCNR and PC 60 BM951. Thus, the presence of two strong electron-withdrawing –CN groups might have electrostatic-attractions with PC 60 BM which improves the film-morphology of the blended active layers and ultimately increases the photocurrent-density for the better performance of solar cell devices52.…”

“…Organic chromophores with aromatic fumaronitrile-core have attracted a significant attention in electroluminescent (EL) devices due to their efficient emission properties in the solid state678. The presence of diphenylfumaronitrile-core greatly reduces the fluorescence quenching in the solid state because of the interaction of anti-parallel dipoles910. In last decade, a lot of substantial efforts have been performed for improving the device performances of solution-processed small molecule organic solar cells (SMOSCs) and attained the high PCE through the development of organic photoactive elecctron-donor materials1112.…”

Barrierless Single‐Electron‐Induced cis–trans Isomerization

“…Unfortunately,amore quantitative evaluation of the lifetime of Feshbach resonances for am olecule of this size is still not possible.W en ote that recent photodetachment experiments have provided evidence for the existence of an electronic resonance in the FN À anion. [16] Thetwo anionic PECs (Figure 1) cross at adihedral angle of 908 8.T his is as ymmetry-allowed crossing of two states of different symmetry,a nd any displacement along one of the non-totally symmetric modes would lead to the formation of aconical intersection (CI). Since the ground states of FN À and MN À anions also have the C 2 point group as as ubgroup and the reaction is barrierless along the symmetry-preserving path, we do not expect much losses to the other isomer through the CI.…”