Effects of Natural Cyclodextrins on the Photophysical Properties of Dibenzofuran-2-carboxylic Acid

2004 ◽  
Vol 108 (3) ◽  
pp. 392-402 ◽  
Author(s):  
Pablo R. Sainz-Rozas ◽  
José Ramón Isasi ◽  
Miguel Sánchez ◽  
Gloria Tardajos
Keyword(s):  
Carboxylic Acid ◽  
Photophysical Properties

Crystal Structures and Photophysical Properties of 9-Anthracene Carboxylic Acid Derivatives for Photomechanical Applications

2011 ◽  
Vol 11 (11) ◽  
pp. 4975-4983 ◽  
Author(s):  
Lingyan Zhu ◽  
Rabih O. Al-Kaysi ◽  
Robert J. Dillon ◽  
Fook S. Tham ◽  
Christopher J. Bardeen
Keyword(s):  
Carboxylic Acid ◽  
Crystal Structures ◽  
Photophysical Properties

Cyclometalated Ir(III) Complexes Containing Pyrazole/Pyrazine Carboxylate Ligands

2011 ◽  
Vol 64 (5) ◽  
pp. 561 ◽  
Author(s):  
Tanima Hajra ◽  
Jitendra K. Bera ◽  
Vadapalli Chandrasekhar
Keyword(s):  
Carboxylic Acid ◽  
Dicarboxylic Acid ◽  
Room Temperature ◽  
Photophysical Properties ◽  
Emission Spectra ◽  
Carboxylate Ligands ◽  
Ancillary Ligands

Two cyclometalated Ir(iii) complexes using 2-phenylpyridine (ppy-H) as the cyclometalating ligand, and pyrazole-3-carboxylic acid (prca-H) and pyrazine 3,5-dicarboxylic acid (pzdca-H2) as ancillary ligands; were synthesized from the chloro-bridged dimer precursor [{(ppy)2Ir}2(μ-Cl)2]. The title compounds [Ir(ppy)2(prca)] (1) and [{Ir(ppy)2}2(pzdca)] (2) are monomeric and dimeric neutral Ir(iii) complexes, respectively. Their electrochemical and photophysical properties were examined. They exhibit metal-based oxidations and ligand-based reductions. These complexes exhibit emission in the blue-green region with lifetimes in the micro-second range at room temperature. The nature of the emission spectra indicates differences in the origin of emission in these two compounds.

scholarly journals The remarkable influence of M2δ to thienyl π conjugation in oligothiophenes incorporating MM quadruple bonds

2008 ◽  
Vol 105 (40) ◽  
pp. 15247-15252 ◽  
Author(s):  
G. T. Burdzinski ◽  
M. H. Chisholm ◽  
P.-T. Chou ◽  
Y.-H. Chou ◽  
F. Feil ◽  
...  
Keyword(s):  
Thin Films ◽  
Carboxylic Acid ◽  
Energy Gap ◽  
Photophysical Properties ◽  
Visible Region ◽  
Triplet States ◽  
Relaxation Dynamics ◽  
Dual Emission ◽  
Molybdenum Complexes ◽  
Quadruple Bonds

Oligothiophenes incorporating MM quadruple bonds have been prepared from the reactions between Mo2(TiPB)4 (TiPB = 2,4,6-triisopropyl benzoate) and 3′,4′-dihexyl-2,2′-:5′,2″-terthiophene-5,5″-dicarboxylic acid. The oligomers of empirical formula Mo2(TiPB)2(O2C(Th)-C4(n-hexyl)2S-(Th)CO2) are soluble in THF and form thin films with spin-coating (Th = thiophene). The reactions between Mo2(TiPB)4 and 2-thienylcarboxylic acid (Th-H), 2,2′-bithiophene-5-carboxylic acid (BTh-H), and (2,2′:5′,2″-terthiophene)-5-carboxylic acid (TTh-H) yield compounds of formula trans-Mo2(TiPB)2L2, where L = Th, BTh, and TTh (the corresponding thienylcarboxylate), and these compounds are considered as models for the aforementioned oligomers. In all cases, the thienyl groups are substituted or coupled at the 2,5 positions. Based on the x-ray analysis, the molecular structure of trans-Mo2(TiPB)2(BTh)2 reveals an extended Lπ-M2δ-Lπ conjugation. Calculations of the electronic structures on model compounds, in which the TiPB are substituted by formate ligands, reveal that the HOMO is mainly attributed to the M2δ orbital, which is stabilized by back-bonding to one of the thienylcarboxylate π* combinations, and the LUMO is an in-phase combination of the thienylcarboxylate π* orbitals. The compounds and the oligomers are intensely colored due to M2δ–thienyl carboxylate π* charge transfer transitions that fall in the visible region of the spectrum. For the molybdenum complexes and their oligomers, the photophysical properties have been studied by steady-state absorption spectroscopy and emission spectroscopy, together with time-resolved emission and transient absorption for the determination of relaxation dynamics. Remarkably, THF solutions the molybdenum complexes show room-temperature dual emission, fluorescence and phosphorescence, originating mainly from 1MLCT and 3MM(δδ*) states, respectively. With increasing number of thienyl rings from 1 to 3, the observed lifetimes of the 1MLCT state increase from 4 to 12 ps, while the phosphorescence lifetimes are ≈80 μs. The oligomers show similar photophysical properties as the corresponding monomers in THF but have notably longer-lived triplet states, ≈200 μs in thin films. These results, when compared with metallated oligothiophenes of the later transition elements, reveal that M2δ–thienyl π conjugation leads to a very small energy gap between the 1MLCT and 3MLCT states of <0.6 eV.

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