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ABSTRACT: Molecular triads based on bis-porphyrin-anthraquinone having azomethine-bridge at the pyrrole-β position have been designed and synthesized. Both free-base AQ-(H2)2 and zinc AQ-(Zn)2 triads are characterized by elemental analysis, MALDI-MS, 1H-NMR, UV-Visible and fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical method. The absorption spectra of both Soret and Q-bands of the triads are red-shifted by 12-20 nm with respect to their monomer units. The study supported by theoretical calculations manifest that there exists a negligible electronic communication in the ground state between the donor porphyrin and acceptor anthraquinone of these triads. However, interestingly, both the triads exhibit significant fluorescence emission quenching (51-92%) of the porphyrin emission compared to their monomeric units. The emission quenching is attributed to the excited state intramolecular photoinduced electron transfer from porphyrins to anthraquinone. The electron transfer rates (kET) of these triads are found in the range 1.0 x 108 to 7.7 x 109 s-1 and are found to be solvent dependent.
The Journal of Physical Chemistry A 03/2013; · 2.95 Impact Factor
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ABSTRACT: Two new heteroleptic ruthenium(II) photosensitizers that contains 2,2';6,2''-terpyridine with extended π-conjugation with donor groups, a 4,4'-dicarboxylic acid-2,2'-bipyridine anchoring ligand and a thiocyanate ligand have been designed, synthesized and fully characterized by CHN, mass spectrometry, UV-vis and fluorescence spectroscopies and cyclic voltammetry. The new sensitizers have either 3,5-di-tert-butyl phenyl (m-BL-5) or triphenylamine (m-BL-6) groups, where the molar extinction coefficient of both the sensitizers is higher than the analogous ruthenium dyes. Both the sensitizers were tested in dye-sensitized solar cells using two different redox electrolytes.
Dalton Transactions 03/2011; 40(17):4497-504. · 3.84 Impact Factor
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ABSTRACT: We prepared two heterooligomeric arrays based on free base/metalloporphyrins at axial positions and a metalloid phthalocyanine as a basal scaffolding unit by using the axial-bonding capabilities as well as the known oxophilicity of dihydroxytin(IV) phthalocyanine. Both heterotrimers were completely characterized by elemental analysis, MALDI-TOF MS, and 1H NMR (one- and two-dimensional), UV/Vis, and fluorescence spectroscopy as well as cyclic voltammetry. The ground-state properties indicate that there is minimal pi-pi interaction between the macrocyclic units. The excited-state properties show that there is electronic energy transfer competing with photoinduced electron transfer from the singlet state of the axial porphyrin to the central metalloid phthalocyanine and a photoinduced electron transfer from the ground state of the axial porphyrin to the singlet state of the central metalloid phthalocyanine.
Chemistry - An Asian Journal 01/2008; 2(12):1574-80. · 4.50 Impact Factor
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Paidi Yella Reddy, Lingamallu Giribabu,
Christopher Lyness,
Henry J Snaith,
Challuri Vijaykumar,
Malapaka Chandrasekharam,
Mannepalli Lakshmikantam,
Jun-Ho Yum,
Kuppuswamy Kalyanasundaram,
Michael Grätzel,
Mohammad K Nazeeruddin
Angewandte Chemie International Edition 02/2007; 46(3):373-6. · 13.45 Impact Factor
