Skii Matrix Research Articles

Reassignment of the electronic states of the trans dimer of acenaphthylene

The fluorescence and excitation spectra of trans dimer of acenaphthylene in a shpol'skii matrix at 4K are reported. The spectra at 4k are compared with the fluorescence and excitation spectra at 77K, previously reported by us. A reassignment of the origin of the two electronic states is required by such a comparison. The comparison once again establishes the point that the g state is below the u state, as was originally found from the comparison of two-photon and one-photon spectra. However, the splitting, which was originally described as “exciton splitting” should actually be ascribed to “site splitting”. The “exciton splitting”, as given in the present study, is about 130 cm −1.

Proton-transfer spectroscopy of 3-hydroxyflavone in an isolated-site crystal matrix.

The isolated-site low-temperature crystal matrix (dilute solutions in heptane and in octane) ( Shpol ' skii matrix) is shown to be operative for the spectroscopic study of 3- hydroxyflavone luminescence. The observed luminescence is demonstrated to be unique proton-transfer fluorescence from the excited tautomer. A separate study at higher concentrations of aggregated molecule luminescence and excitation spectra distinguishes these for 3- hydroxyflavone from isolated-molecule spectra. The application of the Shpol ' skii matrix low-temperature spectroscopy technique is suggested for other large heteroaromatic molecules, such as biomolecules containing polar groups that impart low solubility in nonaqueous solvents.

Anisotropic spin—lattice relaxation in the triplet state of naphtralene- h8 in n-pentane

The temperature dependence of the individual spin—lattice relaxation rate constants ( W ij ) between the lowest triplet sublevels of naphthalene- h 8 in a polycrystalline Shpol'skii matrix of n-pentane have been measured between 1.2 and 2.4 K in zero field. The total sublevel decay constants are evaluated and found to be independent of temperature. The W ij are found to be highly anisotropic, but the anisotropy pattern differs from that observed previously in a durene matrix.

Highly resolved optical spectra of a 2,3-naphthoquinodimethane derivative in a Shpol'skii matrix

The Shpol'skii method yields quasilinear spectra of exo-naphtho [b:3,4] tricyclo [4.2.1.0. 2,5] nonane 5 in n-hexane at 5 K. This result is discussed with reference to the “key and hole” rule. Highly resolved spectra of the 2,3-naphthoquinodimethane derivative 4 are obtained by photolysis of 5. The results are comparable with those of o-durylene 3.

ChemInform Abstract: ELECTRON SPIN‐LATTICE RELAXATION IN THE PHOSPHORESCENT STATE OF XANTHIONE

Spin‐lattice relaxation in the phosphorescent T1 state of xanthione has been measured at 1.0 K in a dilute n‐hexane matrix. Direct excitation of the T1z←S0 transition with a laser pulse of 10−8 s width was followed by observation of the phosphorescence decay monitoring either a T1z or T1y emission band. These bands are optically resolved in the n‐hexane Shpol’skii matrix because of the large zero‐field splitting, D=−15.5 cm−1. Depopulation of T1z by the spin‐lattice relaxation processes, T1z∼≳T1x, T1y was found to be complete within 10−7 s, the time resolution of the measurement. The relaxation process, which at 1.0 K requires the spontaneous creation of a lattice phonon of 15.5 cm−1, is unusually efficient. Thus, when the T1 state is populated by intersystem crossing using either S1←S0, or S2←S0 optical pumping, lack of observed T1z phosphorescence at 1.0 K does not imply that the lower T1x and T1y sublevels are selectively populated. Observation of T1z emission at higher bath temperatures, ∼3.3 K, follo...

ChemInform Abstract: FLUORESCENCE AND FLUORESCENCE EXCITATION SPECTRA OF 1‐AMINOANTHRAQUIONONE IN AN N‐HEPTANE SHPOL′SKII MATRIX

Chemischer InformationsdienstVolume 14, Issue 35 Physical Organic Chemistry ChemInform Abstract: FLUORESCENCE AND FLUORESCENCE EXCITATION SPECTRA OF 1-AMINOANTHRAQUIONONE IN AN N-HEPTANE SHPOL′SKII MATRIX T. P. CARTER, T. P. CARTERSearch for more papers by this authorM. H. VAN BENTHEM, M. H. VAN BENTHEMSearch for more papers by this authorG. D. GILLISPIE, G. D. GILLISPIESearch for more papers by this author T. P. CARTER, T. P. CARTERSearch for more papers by this authorM. H. VAN BENTHEM, M. H. VAN BENTHEMSearch for more papers by this authorG. D. GILLISPIE, G. D. GILLISPIESearch for more papers by this author First published: August 30, 1983 https://doi.org/10.1002/chin.198335048AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue35August 30, 1983 RelatedInformation

Electron spin-lattice relaxation in the phosphorescent state of xanthione

Spin-lattice relaxation in the phosphorescent T1 state of xanthione has been measured at 1.0 K in a dilute n-hexane matrix. Direct excitation of the T1z←S0 transition with a laser pulse of 10−8 s width was followed by observation of the phosphorescence decay monitoring either a T1z or T1y emission band. These bands are optically resolved in the n-hexane Shpol’skii matrix because of the large zero-field splitting, D=−15.5 cm−1. Depopulation of T1z by the spin-lattice relaxation processes, T1z∼≳T1x, T1y was found to be complete within 10−7 s, the time resolution of the measurement. The relaxation process, which at 1.0 K requires the spontaneous creation of a lattice phonon of 15.5 cm−1, is unusually efficient. Thus, when the T1 state is populated by intersystem crossing using either S1←S0, or S2←S0 optical pumping, lack of observed T1z phosphorescence at 1.0 K does not imply that the lower T1x and T1y sublevels are selectively populated. Observation of T1z emission at higher bath temperatures, ∼3.3 K, following a T1z←S0 pulse reveals a peculiar initial rise in intensity followed by an eventual decay. This behavior is explained in terms of lattice heating which accompanies the radiationless T1∼≳S0 decay. The initial increase in intensity results from a thermal pumping rate from the lower energy sublevels which exceeds the overall decay rate of the T1 state. Nonexponential decay of the T1y emission is explained by the same model. We find that the T1z emission intensity vs time cannot be explained quantitatively by a uniform lattice temperature during the decay, but that temperature gradients must be present.

ChemInform Abstract: INTRAMOLECULAR HYDROGEN BONDING. 2. ENORMOUS DEUTERIUM ISOTOPE EFFECT ON THE PHOSPHORESCENCE OF 6‐HYDROXYBENZANTHRONE

The laser-excited fluorescence and phosphorescence spectra of the title compound and its hydroxy-deuterated analogue have been measured in an n-hexane Shpol'skii matrix at 10 K. The deuterium substitution has only a minor effect on the fluorescence intensity and the fluorescence and phosphorescence vibronic patterns but leads to a greater than order of magnitude increase in the phosphorescence quantum yield. The phosphorescence lifetimes have been measured to be 19 ms for the normal isotopic species and 300 ms for the deuterated form. This probably represents the largest deuterium isotope effect yet observed in aromatic molecule photophysics.

Identification of triaromatic azaarenes in crude oils by high-resolution spectrofluorometry in Shpol'skii matrixes

Identification of triaromatic azaarenes in crude oils by high-resolution spectrofluorometry in Shpol'skii matrixes

ChemInform Abstract: SITE‐SELECTED FLUORESCENCE STUDY OF ANTHRACENE AND ITS HALOGENATED DERIVATIVES IN SHPOL′SKII MATRIXES

Chemischer InformationsdienstVolume 13, Issue 41 Physical Organic Chemistry ChemInform Abstract: SITE-SELECTED FLUORESCENCE STUDY OF ANTHRACENE AND ITS HALOGENATED DERIVATIVES IN SHPOL′SKII MATRIXES T. P. CARTER, T. P. CARTERSearch for more papers by this authorG. D. GILLISPIE, G. D. GILLISPIESearch for more papers by this author T. P. CARTER, T. P. CARTERSearch for more papers by this authorG. D. GILLISPIE, G. D. GILLISPIESearch for more papers by this author First published: October 12, 1982 https://doi.org/10.1002/chin.198241055AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue41October 12, 1982 RelatedInformation

Intramolecular hydrogen bonding. 2. Enormous deuterium isotope effect on the phosphorescence of 6-hydroxybenzanthrone

The laser-excited fluorescence and phosphorescence spectra of the title compound and its hydroxy-deuterated analogue have been measured in an n-hexane Shpol'skii matrix at 10 K. The deuterium substitution has only a minor effect on the fluorescence intensity and the fluorescence and phosphorescence vibronic patterns but leads to a greater than order of magnitude increase in the phosphorescence quantum yield. The phosphorescence lifetimes have been measured to be 19 ms for the normal isotopic species and 300 ms for the deuterated form. This probably represents the largest deuterium isotope effect yet observed in aromatic molecule photophysics.

Site-selected fluorescence study of anthracene and its halogenated derivatives in Shpol'skii matrixes

Site-selected fluorescence study of anthracene and its halogenated derivatives in Shpol'skii matrixes

Molecular spectroscopy of 2,5-distyrylpyrazine

The molecular absorption and fluorescence spectra of 2,5-distyrylpyrazine (DSP) in a Shpol'skii matrix at 4 K together with the Raman spectrum of crystalline samples at 298 K have been investigated. The transition to the lowest excited singlet state of B u symmetry is of π—π * character and two sites with origins at 23621 cm −1 and 23713 cm −1 are observed in n-tetradecane at 4 K. The DSP molecule has the same conformation in the two sites and, furthermore, the geometry of the molecule in the first excited singlet states is unchanged as compared to the ground state. The vibrational progression observed for DSP is compared with the literature data for distyrylbenzene (DSB) and slilbene.

Spectroscopic investigation of the origin of distortion of guest coronene in various sites of n-heptane Shpol'skii matrix

We report the high resolution emission (S1 → S0, T1 → S0) and laser single site singlet excitation (S1 ← S0) spectra for the various insertion sites of coronene in n-heptane cooled to 1.5 K. The observation of site splitting of doubly degenerate vibrations and weak electric dipole forbidden 0, 0 bands in the S1 → S0 and T1 → S0 spectra indicates that the ground state, the first excited singlet and lowest triplet states are all distorted. In these spectra, the intensity distribution of the various sites in the 0, 0 bands suggests that the distortion is different from site to site but similar in S0, S1 and T1. Identical ordering of the sites in S1 S0 and S1 S0 spectra as well as the observation of weak shifts in the vibrational frequencies in the two states implies the absence of strong pseudo Jahn-Teller forces in the first excited singlet state. We propose, further, that this is also true for the triplet state. This conclusion is supported by the similarity in zero-field splitting parameters of coronene and deuterated coronene. Taken together, these results indicate strongly that the distortion of coronene in n-heptane is primarily crystal field induced and is not greatly changed upon excitation of the molecule to its lowest excited states.

Laser-induced photochemical isomerization of free base porphyrin in ann-octane crystal at 4·2 K

It is known that the porphyrin free base (H2P) can be incorporated in an n-octane Shpol'skii matrix. In slowly grown crystals the solute molecules occur in two orientations, which are co-planar and have their N-H … H-N axes at right angles; in the S 1↔S 0 ‘quasi-line’ absorption and fluorescence spectra they can be distinguished by a relative shift of 65 cm-1 of their spectral features. By irradiation with light the two species are transformed into one another via a shift of the two inner protons. Here a study is presented of the photoisomerism following selective excitation with a dye laser into the 0-0 band of the S 1←S 0 transition of either of the two forms, for H2P and D2P (two inner hydrogens replaced by deuterium). At 4·2 K the reaction proceeds in both directions; for H2P the reaction in one direction appears to be 10 per cent faster than in the other, for D2P the absolute rates are nearly ten times lower than for H2P and not measurably different in the two directions. The reactions are not signif...

Vibronic interactions and environmental effects on the phosphorescent state of 9,10-anthraquinone in Shpol'skii matrixes at 4.2 K

Vibronic interactions and environmental effects on the phosphorescent state of 9,10-anthraquinone in Shpol'skii matrixes at 4.2 K

Excimer and photochemically induced fluorescence of 9-cyanoanthracene crystals

The polarized emission spectra of melt and vapor grown single crystals of carefully purified 9-cyanoanthracene (9-CNA) are reported. This materials has a quasi one-dimensional structure with molecules stacked along the c-axis. In crystals previously unirradiated at room temperature, the emission is excimer-like with a double peak (550 nm, E⊥ c) and (525 nm, E| c) at 2 K, and a single peak at 300 K (588 nm, E, | c). Exposure to UV radiation at room temperature induces fluorescence associated with the production of photodimers. At 2 K this fluorescence is highly structured and coexists with excimer emission. It also extends to higher energies than the origin of the exciton band of the first singlet, supporting a model in which this component of the fluorescence arises from 9-CNA molecules separated from bulk by a matrix of photodimers. The photoproduct thus acts somewhat like a Shpol'skii matrix for these unreacted molecules.