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Shilov RA, Podkorytov IS, Kisel KS, Galenko EE, Karpitskaya DO, Rodionov IA, Shakirova JR, Tunik SP. DPPM-Bridged Binuclear Pt(II) Pincer Complexes: Chemistry, Structure, and Photophysics in Solution Revisited. Inorg Chem 2024; 63:11194-11208. [PMID: 38836300 DOI: 10.1021/acs.inorgchem.4c00984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2024]
Abstract
A series of luminescent binuclear ([dppm{Pt(NNC)}2]2+) and mononuclear ([PPh3Pt(NNC)]+) complexes containing pincer ligands were synthesized and characterized. Photophysical characteristics of both types of complexes were studied in dichloromethane solution. In the solid phase, the binuclear compounds adopt a syn configuration where the {Pt(NNC)} fragments are held together due to intramolecular Pt-Pt bonding and π-stacking of the pincer ligand aromatic systems. Analysis of the complexes' molecular structure in solution by multinuclear NMR spectroscopy showed that the stacked intramolecular configuration is retained in fluid media, which is in complete agreement with a considerable red shift of the emission wavelength due to formation of the intramolecular Pt-Pt bond, leading to the transformation of an emissive excited state to 3MMLCT. It was also found that triethylamine quenches the emission of both types of complexes; the mechanism of quenching is a combination of dynamic and static channels of excited-state deactivation. In the case of binuclear complexes, deprotonation of the dppm methylene bridge by triethylamine also contributes to the chromophore quenching. To explain the observed chemistry of binuclear complex interactions with Et3N, a chemical equilibrium scheme was suggested, which was confirmed by quantitative monitoring of the 31P signal variations as a function of triethylamine concentration.
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Affiliation(s)
- Roman A Shilov
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Ivan S Podkorytov
- Biomolecular NMR Laboratory, St. Petersburg State University, 7-9 Universitetskaya Emb., 199034 Saint Petersburg, Russia
| | - Kristina S Kisel
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Ekaterina E Galenko
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Daria O Karpitskaya
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Ivan A Rodionov
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Julia R Shakirova
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
| | - Sergey P Tunik
- Institute of Chemistry, St. Petersburg State University, Universitetskii av., 26, 198504 Saint Petersburg, Russia
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Lopes J, Machado A, Batista A, Araujo P, Barbosa Neto N. Protonation, exciplex, and evidence of aggregate formation in meso-tetra(4-pyridyl) porphyrin triggered by excited-state absorption. J Photochem Photobiol A Chem 2022. [DOI: 10.1016/j.jphotochem.2021.113759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Kuzmin MG, Soboleva IV, Dolotova EV, Dogadkin DN. Peculiarities and paradoxes of photoinduced electron transfer reactions. HIGH ENERGY CHEMISTRY 2011. [DOI: 10.1134/s0018143911050122] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Abstract
Transient exciplex formation mechanism of excited-state electron transfer reactions is analyzed in terms of experimental data on thermodynamics and kinetics of exciplex formation and decay. Experimental profiles of free energy, enthalpy, and entropy for transient exciplex formation and decay are considered for several electron transfer reactions in various solvents. Strong electronic coupling in contact pairs of reactants causes substantial decrease of activation energy relative to that for conventional long-range ET mechanism, especially for endergonic reactions, and provides the possibility for medium reorganization concatenated to gradual charge shift in contrast to conventional preliminary medium and reactants reorganization. Experimental criteria for transient exciplex formation (concatenated) mechanism of excited-state electron transfer are considered. Available experimental data show that this mechanism dominates for endergonic ET reactions and provides a natural explanation for a lot of known paradoxes of ET reactions.
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Collective proton motion in the intramolecular hydrogen bonding network and the consequent enhancement in the acidity of hydroxycalixarenes. J Photochem Photobiol A Chem 2008. [DOI: 10.1016/j.jphotochem.2007.09.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Kuzmin MG, Soboleva IV, Dolotova EV. The behavior of exciplex decay processes and interplay of radiationless transition and preliminary reorganization mechanisms of electron transfer in loose and tight pairs of reactants. J Phys Chem A 2007; 111:206-15. [PMID: 17214455 DOI: 10.1021/jp066379e] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Exciplex emission spectra and rate constants of their decay via internal conversion and intersystem crossing are studied and discussed in terms of conventional radiationless transition approach. Exciplexes of 9-cyanophenanthrene with 1,2,3-trimethoxybenzene and 1,3,5-trimethoxybenzene were studied in heptane, toluene, butyl acetate, dichloromethane, butyronitrile, and acetonitrile. A better description of spectra and rate constants is obtained using 0-0 transition energy and Gauss broadening of vibrational bands rather than the free energy of electron transfer and reorganization energy. The coincidence of parameters describing exciplex emission spectra and dependence of exciplex decay rate constants on energy gap gives the evidence of radiationless quantum transition mechanism rather than thermally activated medium reorganization mechanism of charge recombination in exciplexes and excited charge transfer complexes (contact radical ion pairs) as well as in solvent separated radical ion pairs. Radiationless quantum transition mechanism is shown to provide an appropriate description also for the main features of exergonic excited-state charge separation reactions if fast mutual transformations of loose and tight pairs of reactants are considered. In particular, very fast electron transfer (ET) in tight pairs of reactants with strong electronic coupling of locally excited and charge transfer states can prevent the observation of an inverted region in bimolecular excited-state charge separation even for highly exergonic reactions.
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Affiliation(s)
- Michael G Kuzmin
- Department of Chemistry, Moscow State Lomonosov University, Moscow 119992, Russia.
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Lazarides T, Alamiry MAH, Adams H, Pope SJA, Faulkner S, Weinstein JA, Ward MD. Anthracene as a sensitiser for near-infrared luminescence in complexes of Nd(iii), Er(iii) and Yb(iii): an unexpected sensitisation mechanism based on electron transfer. Dalton Trans 2007:1484-91. [PMID: 17404649 DOI: 10.1039/b700714k] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ligand L(1), which contains a chelating 2-(2-pyridyl)benzimidazole (PB) unit with a pendant anthacenyl group An connected via a methylene spacer, (L(1) = PB-An), was used to prepare the 8-coordinate lanthanide(III) complexes [Ln(hfac)(3)(L(1))] (Ln = Nd, Gd, Er, Yb) which have been structurally characterised and all have a square antiprismatic N(2)O(6) coordination geometry. Whereas free L(1) displays typical anthracene-based fluorescence, this fluorescence is completely quenched in its complexes. The An group in L(1) acts as an antenna unit: in the complexes [Ln(hfac)(3)(L(1))] (Ln = Nd, Er, Yb) selective excitation of the anthracene results in sensitised near-infrared luminescence from the lanthanide centres with concomitant quenching of An fluorescence. Surprisingly, the anthracene fluorescence is also quenched even in the Gd(III) complex and in its Zn(II) adduct in which quenching via energy transfer to the metal centre is not possible. It is proposed that the quenching of anthracene fluorescence in coordinated L(1) arises due to intra-ligand photoinduced electron-transfer from the excited anthracene chromophore (1)An* to the coordinated PB unit generating a short-lived charge-separated state [An(.+)-PB(.-)] which collapses by back electron-transfer to give (3)An*. This electron-transfer step is only possible upon coordination of L(1) to the metal centre, which strongly increases the electron acceptor capability of the PB unit, such that (1)An* --> PB PET is endoergonic in free L(1) but exergonic in its complexes. Thus, rather than a conventional set of steps ((1)An* -->(3)An* --> Ln), the sensitization mechanism now includes (1)An* --> PB photoinduced electron transfer to generate charge-separated [An(.+)-PB(.-)], then back electron-transfer to generate (3)An* which finally sensitises the Ln(III) centre via energy transfer. The presence of (3)An* in L(1) and its complexes is confirmed by nanosecond transient absorption studies, which have also shown that the (3)An* lifetime in the Nd(III) complex matches the rise time of Nd-centred near-infrared emission, confirming that the final step of the sequence is (3)An* --> Ln(III) energy-transfer.
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Kuzmin MG, Soboleva IV, Dolotova EV. Competition of concatenated and thermally activated medium reorganization in photoinduced electron transfer reactions. HIGH ENERGY CHEMISTRY 2006. [DOI: 10.1134/s0018143906040072] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Photochemical reactions of electron-deficient olefins with N,N,N′,N′-tetramethylbenzidine via photoinduced electron-transfer. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.06.049] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Dossot M, Allonas X, Jacques P. Singlet Exciplexes between a Thioxanthone Derivative and Substituted Aromatic Quenchers: Role of the Resonance Integral. Chemistry 2005; 11:1763-70. [PMID: 15669045 DOI: 10.1002/chem.200400269] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Fluorescence quenching of a thioxanthone derivative by methyl- and methoxy-substituted benzenes (MeB and MeOB, respectively) is performed in solvents of different polarity. Emissive exciplexes are observed even in polar solvents and provide kinetic and spectroscopic data over a large scale of solvent polarity. These data were subsequently analyzed by use of a new theoretical model that leads to a thermodynamic relationship between exciplex and electron-transfer driving forces Delta G(exc) and Delta G(et), respectively. The remarkable agreement found between this model and both kinetic and spectroscopic data supports its validity. Moreover, the difference observed between MeB and MeOB compounds in quenching efficiency is analyzed by this model and provides the main parameters governing exciplex features, especially the resonance integral between locally excited and charge-transfer states.
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Affiliation(s)
- Manuel Dossot
- Department of Photochemistry, Université de Haute Alsace, 3, rue Alfred Werner, 68093 Mulhouse Cedex, France
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The nature of internal conversion and intersystem crossing in exciplexes. HIGH ENERGY CHEMISTRY 2005. [DOI: 10.1007/s10733-005-0018-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Lai RY, Bard AJ. Electrogenerated Chemiluminescence. 70. The Application of ECL to Determine Electrode Potentials of Tri-n-propylamine, Its Radical Cation, and Intermediate Free Radical in MeCN/Benzene Solutions. J Phys Chem A 2003. [DOI: 10.1021/jp026743j] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rebecca Y. Lai
- Department of Chemistry and Biochemistry, The University of Texas at Austin, Texas 78712-0165
| | - Allen J. Bard
- Department of Chemistry and Biochemistry, The University of Texas at Austin, Texas 78712-0165
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Specific solvent effects on the charge separation efficiency in photoinduced electron transfer processes. J Photochem Photobiol A Chem 2000. [DOI: 10.1016/s1010-6030(00)00197-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Pischel U, Zhang X, Hellrung B, Haselbach E, Muller PA, Nau WM. Fluorescence Quenching of n,π*-Excited Azoalkanes by Amines: What Is a Sterically Hindered Amine? J Am Chem Soc 2000. [DOI: 10.1021/ja992508b] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Uwe Pischel
- Contribution from the Institute of Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Institute of Physical Chemistry, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland
| | - Xiangyang Zhang
- Contribution from the Institute of Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Institute of Physical Chemistry, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland
| | - Bruno Hellrung
- Contribution from the Institute of Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Institute of Physical Chemistry, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland
| | - Edwin Haselbach
- Contribution from the Institute of Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Institute of Physical Chemistry, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland
| | - Pierre-Alain Muller
- Contribution from the Institute of Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Institute of Physical Chemistry, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland
| | - Werner M. Nau
- Contribution from the Institute of Physical Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland, and the Institute of Physical Chemistry, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland
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