Two-photon excitation of substituted enediynes

    Authors

    J. F. Kauffman; J. M. Turner; I. V. Alabugin; B. Breiner; S. V. Kovalenko; E. A. Badaeva; A. Masunov;S. Tretiak

    Comments

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    Abbreviated Journal Title

    J. Phys. Chem. A

    Keywords

    DENSITY-FUNCTIONAL THEORY; DOUBLE-STRAND CLEAVAGE; ANTITUMOR ANTIBIOTIC; DYNEMICIN; THERMAL BERGMAN CYCLIZATION; ABSORPTION CROSS-SECTIONS; AROMATIC NITRO-COMPOUNDS; SILYL ENOL ETHERS; DNA-CLEAVAGE; PHOTOCHEMICAL; CYCLOAROMATIZATION; SYNTHETIC EQUIVALENTS; Chemistry, Physical; Physics, Atomic, Molecular & Chemical

    Abstract

    Electronic spectroscopy of nine benzannelated enediynes and a related fulvene was studied under one-photon and two-photon excitation conditions. We utilize measured absorbance and emission spectra and time-resolved fluorescence decays of these molecules to calculate their radiative lifetimes and fluorescence quantum yields. The fluorescence quantum yields for the other compounds were referenced to the fluorescence quantum yield of compound 3 and used to determine relative two-photon absorption cross-sections. Further insight into experimental studies has been achieved using time-dependent density functional (TD-DFT) computations. The probability of two-photon absorption (TPA) increases noticeably for excitation to the higher excited states. The photophysical properties of benzannelated enediynes are sensitive to substitutions at both the core and the periphery of the enediyne chromophore. Considerably enhanced two-photon absorption is observed in an enediyne with donor substitution in the middle and acceptor substitution at the termini. Excited states with B symmetry are not active in TPA spectra. From a practical point of view, this study extends the range of wavelengths applicable for activation of the enediyne moiety from 350 to 600 nm and provides a rational basis for future studies in this field. Our theoretical computations confirmed that lowest energy TPA in benzannelated enediynes involves different orbitals than lowest energy one-photon absorbance and provided further support to the notion that introduction of donor and acceptor substituents at different ends of a molecule increases TPA.

    Journal Title

    Journal of Physical Chemistry A

    Volume

    110

    Issue/Number

    1

    Publication Date

    1-1-2006

    Document Type

    Article

    Language

    English

    First Page

    241

    Last Page

    251

    WOS Identifier

    WOS:000234520300031

    ISSN

    1089-5639

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