Triplet excited state properties in variable gap π-conjugated donor-acceptor-donor chromophores

被引:65
作者
Cekli, Seda [1 ,2 ]
Winkel, Russell W. [1 ,2 ]
Alarousu, Erkki [3 ]
Mohammed, Omar F. [3 ]
Schanze, Kirk S. [1 ,2 ]
机构
[1] Univ Florida, Dept Chem, Gainesville, FL 32611 USA
[2] Univ Florida, Ctr Macromol Sci & Engn, Gainesville, FL 32611 USA
[3] King Abdullah Univ Sci & Technol, Div Phys Sci & Engn, Solar & Photovolta Engn Res Ctr, Thuwal 239556900, Saudi Arabia
基金
美国国家科学基金会;
关键词
INTERSYSTEM CROSSING RATE; CHARGE-TRANSFER STATES; OPTICAL-PROPERTIES; SINGLET-STATE; POLYMERS; PHOTOPHYSICS; MOLECULES; ENERGY; DERIVATIVES; OXYGEN;
D O I
10.1039/c5sc04578a
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A series of variable band-gap donor-acceptor-donor (DAD) chromophores capped with platinum(II) acetylide units has been synthesized and fully characterized by electrochemical and photophysical methods, with particular emphasis placed on probing triplet excited state properties. A counter-intuitive trend of increasing fluorescence quantum efficiency and lifetime with decreasing excited state energy (optical gap) is observed across the series of DAD chromophores. Careful study of the excited state dynamics, including triplet yields (as inferred from singlet oxygen sensitization), reveals that the underlying origin of the unusual trend in the fluorescence parameters is that the singlet-triplet intersystem crossing rate and yield decrease with decreasing optical gap. It is concluded that the rate of intersystem crossing decreases as the LUMO is increasingly localized on the acceptor unit in the DAD chromophore, and this result is interpreted as arising because the extent of spin-orbit coupling induced by the platinum heavy metal centers decreases as the LUMO is more localized on the acceptor. In addition to the trend in intersystem crossing, the results show that the triplet decay rates follow the Energy Gap Law correlation over a 1.8 eV range of triplet energy and 1000-fold range of triplet decay rates. Finally, femtosecond transient absorption studies for the DAD chromophores reveals a strong absorption in the near-infrared region which is attributed to the singlet excited state. This spectral band appears to be general for DAD chromophores, and may be a signature of the charge transfer (CT) singlet excited state.
引用
收藏
页码:3621 / 3631
页数:11
相关论文
共 55 条
[1]   Design of organic molecules with large two-photon absorption cross sections [J].
Albota, M ;
Beljonne, D ;
Brédas, JL ;
Ehrlich, JE ;
Fu, JY ;
Heikal, AA ;
Hess, SE ;
Kogej, T ;
Levin, MD ;
Marder, SR ;
McCord-Maughon, D ;
Perry, JW ;
Röckel, H ;
Rumi, M ;
Subramaniam, C ;
Webb, WW ;
Wu, XL ;
Xu, C .
SCIENCE, 1998, 281 (5383) :1653-1656
[2]   The donor-acceptor approach allows a black-to-transmissive switching polymeric electrochrome [J].
Beaujuge, P. M. ;
Ellinger, S. ;
Reynolds, J. R. .
NATURE MATERIALS, 2008, 7 (10) :795-799
[3]   Spectral Engineering in π-Conjugated Polymers with Intramolecular Donor-Acceptor Interactions [J].
Beaujuge, Pierre M. ;
Amb, Chad M. ;
Reynolds, John R. .
ACCOUNTS OF CHEMICAL RESEARCH, 2010, 43 (11) :1396-1407
[4]   Spin-orbit coupling and intersystem crossing in conjugated polymers: A configuration interaction description [J].
Beljonne, D ;
Shuai, Z ;
Pourtois, G ;
Bredas, JL .
JOURNAL OF PHYSICAL CHEMISTRY A, 2001, 105 (15) :3899-3907
[5]  
Busby E, 2015, NAT MATER, V14, P426, DOI [10.1038/nmat4175, 10.1038/NMAT4175]
[6]   Excited state lifetime and intersystem crossing rate of asymmetric pentaazadentate porphyrin-like metal complexes [J].
Byeon, CC ;
McKerns, MM ;
Sun, WF ;
Nordlund, TM ;
Lawson, CM ;
Gray, GM .
APPLIED PHYSICS LETTERS, 2004, 84 (25) :5174-5176
[7]   Electrochemical Considerations for Determining Absolute Frontier Orbital Energy Levels of Conjugated Polymers for Solar Cell Applications [J].
Cardona, Claudia M. ;
Li, Wei ;
Kaifer, Angel E. ;
Stockdale, David ;
Bazan, Guillermo C. .
ADVANCED MATERIALS, 2011, 23 (20) :2367-2371
[8]   APPLICATION OF THE ENERGY-GAP LAW TO THE DECAY OF CHARGE-TRANSFER EXCITED-STATES - SOLVENT EFFECTS [J].
CASPAR, JV ;
SULLIVAN, BP ;
KOBER, EM ;
MEYER, TJ .
CHEMICAL PHYSICS LETTERS, 1982, 91 (02) :91-95
[9]   Photophysics in bipyridyl and terpyridyl platinum(II) acetylides [J].
Castellano, FN ;
Pomestchenko, IE ;
Shikhova, E ;
Hua, F ;
Muro, ML ;
Rajapakse, N .
COORDINATION CHEMISTRY REVIEWS, 2006, 250 (13-14) :1819-1828
[10]   An investigation of the solvent dependence on the ultrafast intersystem crossing kinetics of xanthone [J].
Cavaleri, JJ ;
Prater, K ;
Bowman, RM .
CHEMICAL PHYSICS LETTERS, 1996, 259 (5-6) :495-502