Spectroscopic Studies of 12-Oxo-5(12H)-naphthacenylidene and 7H-Benz[de]anthracen-7-ylidene in Shpolskii Matrixes at 5 K

Abstract

The triplet-triplet fluorescence and fluorescence excitation spectra of two new, planar diaryl carbenes in n-hexane and n-heptane were studied at cryogenic temperatures. Fluorescence decays were fitted to three exponential functions. Fluorescence decays of 12-oxo-5(12H)-naphthacenylidene were sensitive to the presence of a magnetic field, and this dependence allowed the estimation of the zero field splitting parameters (D) of the excited triplet state of this compound, which were 0.037 ( 0.010 and 0.03 ( 0.015 cm -1 for the low-and high-energy sites, respectively. These results are corroborated by computational studies of the ground-state preferences and the triplet excitation energies.

Zero-field Splitting of the Triplet Ground and Excited States of 7H-Benz[de]anthracen-7-ylidene in n-Hexane at 1.7 K: A Hole Burning Study

“…7-BAC in an n-hexane matrix mainly occupies two sites leading to two (0,0) fluorescence excitation spectra origins with maxima at 640.1 and 637.7 nm 9 and full width at half maximum (fwhm) of 4.6 cm -1 , as shown in Figure 1. Hole burning experiments were performed on both of these lines at 1.7 K and typical hole spectra are shown in Figures 2-4.…”

“…7-BAC was obtained in-situ by the photolysis of the 7-diazo-7H-benz[de]anthracene precursor (synthesized in the Columbus Laboratory 9 ) dissolved in n-hexane at 4.2 K. The precursor concentration was about 2 × 10 -3 mol/L. Photolysis was performed with either the 366 or 404 nm line isolated from a mercury lamp.…”

Excited-State Distortions of Cyclometalated Ir(III) Complexes Determined from the Vibronic Structure in Luminescence Spectra

“…Such systems have been widely used to obtain narrow spectral lines from planar aromatic hydrocarbons. [34][35][36][37] In a recent study, sharp line vibronic structure from a planar organometallic compound in a Shpol'skii matrix was reported. 38 It is surprising that an octahedral organometallic ion can be incorporated in a Shpol'skii matrix.…”

Reactive Site Model of the Reduction of SO2 on Graphite

“…6,7 Depending on the model structure, carbenes may have a triplet or a singlet electronic ground state. 8 Zigzag and armchair sites present different reactivity 9,10 while the stability of the carbene and carbyne structures increases with increasing size of the graphene sheet, due to higher resonance energy contributions. 11 Some studies of organic chemistry of solid surfaces allowed to postulate mechanisms such as the dissociation of saturated C−H bonds 12 and the reactivity of alkyl halides 13−18 on solids.…”

“…Consequently, individual graphene layers are used as graphite models, where the main surface functionalities are the free dehydrogenated sites at the zigzag (carbene type) and armchair edges (carbyne type). , Chemisorption of NO and N 2 O were analyzed considering both, the zigzag and armchair edges, as well as the reliability to describe the multiradical nature of the zigzag edge . X-ray diffraction (XRD) and transmission electron microscopy of several anthracites produced consistent experimental results showing that graphene edge sites are not completely saturated with hydrogen. , Depending on the model structure, carbenes may have a triplet or a singlet electronic ground state . Zigzag and armchair sites present different reactivity , while the stability of the carbene and carbyne structures increases with increasing size of the graphene sheet, due to higher resonance energy contributions …”