Self-sensitized photo-oxidation of platinum(II) complexes of 1,10-phenanthroline with 3,4-dimercaptotoluene and thiosalicylic acid by 1O2

Shukla, S.; Kamath, S.S.; Srivastava, T.S.

doi:10.1016/1010-6030(89)85015-4

Cited by 13 publications

(5 citation statements)

References 12 publications

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“…Both transitions were assigned as LLCT, based on the previous work of Miller and Dance, and no emission was detected in solution at room temperature. Pt(bpy)(tdt) and Pt(phen)(tdt) were later studied by Srivastava in the context of 1 O 2 generation by the excited states of the complexes, but no photoluminescence was reported …”

Section: Discussionmentioning

confidence: 99%

Tuning the Excited-State Properties of Platinum(II) Diimine Dithiolate Complexes

1996

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Two series of Pt(diimine)(dithiolate) complexes have been prepared in order to investigate the effects of molecular design on the excited-state properties of this chromophore. The first series comprises Pt(dbbpy)(dithiolate) complexes where dbbpy ) 4,4′-di-tert-butyl-2,2′-bipyridine and the dithiolates are 1-(tert-butylcarboxy)-1-cyanoethylene-2,2-dithiolate (tbcda), 1-diethylphosphonate-1-cyanoethylene-2,2-dithiolate (cpdt), 6,7-dimethylquinoxaline-2,3-dithiolate (dmqdt), maleonitriledithiolate (mnt), and toluene-3,4-dithiolate (tdt). The second series comprises Pt(diimine)(tdt) complexes where the diimines are 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen), 4,4′-di-tert-butyl-2,2′-bipyridine (dbbpy), 4,4′-dimethyl-2,2′-bipyridine (dmbpy), 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 5-chloro-1,10-phenanthroline (Cl-phen), 4,4′-dichloro-2,2′-bipyridine (Cl 2 bpy), and 4,4′-bis(ethoxycarbonyl)-2,2′-bipyridine (EC-bpy). All of the compounds display solvatochromic absorption bands and solution luminescence, which are attributed to a common charge-transfer-to-diimine excited state. The excited-state energies can be tuned by approximately 1 eV through ligand variation. Solution lifetimes range from 1 ns to over 1000 ns and Φ em range from 6.4 × 10 -3 to less than 10 -5 in CH 2 Cl 2 . Based on these data, the nonradiative and radiative decay rate constants have been calculated. For the Pt(diimine)(tdt) series, the nonradiative decay rate constants increase exponentially with decreasing energy, in agreement with the Energy Gap Law, while those for the Pt(dbbpy)(dithiolate) complexes do not exhibit a similar correlation. Excited-state redox potentials have been estimated for all of the complexes from spectroscopic and electrochemical data. The ability to tune the driving force for bimolecular excited-state electron-transfer reactions has been demonstrated for eight of the complexes using reductive and oxidative quenching experiments.

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Section: Discussionmentioning

confidence: 99%

Tuning the Excited-State Properties of Platinum(II) Diimine Dithiolate Complexes

1996

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“…Our group has been studying the photophysics of MLCT and LLCT excited states in transition metal complexes. − During the course of routine photophysical studies on (tbubpy)Pt II (dpdt) and (tbubpy)Pt II (edt) ( 1 and 2 , respectively, where tbubpy = 4,4‘-di- tert -butyl-2,2‘-bipyridine, dpdt = meso -1,2-diphenyl-1,2-ethanedithiolate, and edt = 1,2-ethanedithiolate) we discovered that the two complexes were moderately photochemically reactive in air-saturated solution. Given the previous work in the area, − we were not surprised by the photosensitivity of 1 and 2 in the presence of dioxygen; however, we were intrigued by preliminary results which suggested that 1 and 2 react via different pathways. Thus, we embarked on a study of the photophysics and photoreactivity of the two complexes in an effort to ascertain the reaction products and the pathways by which they form.…”

Section: Introductionmentioning

confidence: 88%

“…While most of the work carried out to date on (NN)Pt II (SS) complexes has focused on the photophysics of the charge transfer to diimine state, several recent reports suggest that the chromophore is also photochemically reactive in oxygenated solution. Thus, in a series of papers Srivastava and co-workers demonstrated that photolysis of (bpy)Pt II (tdt) (bpy = 2,2‘-bipyridine and tdt = 3,4-toluenedithiolate) and several related complexes in the presence of dioxygen leads to decomposition of the complex. − Although the products of the photodecomposition were not determined, several (NN)Pt II (SS) complexes were found to sensitize 1 O 2 * with moderate efficiency. On the basis of this finding it was hypothesized that the photochemical reaction involved oxidation of the dithiolate ligand by 1 O 2 * in a manner consistent with the reactivity of organic thioethers. − …”

Section: Introductionmentioning

confidence: 99%

Photooxidation of Diimine Dithiolate Platinium(II) Complexes Induced by Charge Transfer to Diimine Excitation

1996

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A photochemical and photophysical investigation was carried out on (tbubpy)Pt(II)(dpdt) and (tbubpy)Pt(II)(edt) (1 and 2, respectively, where tbubpy = 4,4'-di-tert-butyl-2,2'-bipyridine, dpdt = meso-1,2-diphenyl-1,2-ethanedithiolate and edt = 1,2-ethanedithiolate). Luminescence and transient absorption studies reveal that these complexes feature a lowest excited state with Pt(S)(2) --> tbubpy charge transfer to diimine character. Both complexes are photostable in deoxygenated solution; however, photolysis into the visible charge transfer band in air-saturated solution induces moderately efficient photooxidation. Photooxidation of 1 produces the dehydrogenation product (tbubpy)Pt(II)(1,2-diphenyl-1,2-ethenedithiolate) (4). By contrast, photooxidation of 2 produces S-oxygenated complexes in which one or both thiolate ligands are converted to sulfinate (-SO(2)R) ligands. Mechanistic photochemical studies and transient absorption spectroscopy reveal that photooxidation occurs by (1) energy transfer from the charge transfer to diimine excited state of 1 to (3)O(2) to produce (1)O(2) and (2) reaction between (1)O(2) and the ground state 1. Kinetic data indicates that excited state 1 produces (1)O(2) efficiently and that reaction between ground state 1 and (1)O(2) occurs with k approximately 3 x 10(8) M(-)(1) s(-)(1).

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“…Also, in the presence of reductive or oxidative quenching molecules, the corresponding ground state [Pt II (diimine • )(dithiolate)] - or [Pt II (diimine)(dithiolate • )] + can be formed via a photoinduced electron-transfer reaction ,, The fundamental basis for the photoinduced electron-transfer reactions of these [Pt II (diimine)(dithiolate)] complexes is that both the diimine-type ligands and the dithiolates are redox-active. The redox-activity of coordination dithiolate ligands is well established by spectroscopic studies (IR, RR, X-ray, EPR, sulfur K-edge XAS) and theoretical (correlated ab initio and density functional) calculations − carried out recently on [M(L) 2 ] z complexes (M = Ni II , Pd II , Pt II , Cu III , Au III ; z = 1+ → 2−; L = 1,2-benzenedithiolate or 1,2-disubstituted 1,2-ethylenedithiolate ligands).…”

Section: Introductionmentioning

confidence: 99%

Dimerization Processes of Square Planar [Pt^II(^tbpy)(dithiolato^•)]⁺ Radicals

Pap¹,

Benedito²,

Bothe³

et al. 2007

Inorg. Chem.

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The preparation and structural characterization of the neutral, square planar complexes [PtII(tbpy)(A)] (1), [PtII(tbpy)(B)] (2), and [PtII(PPh3)2(B)] (3) have been accomplished, where (tbpy) = 4,4'-di-tert-butylpyridine, (A)2- = 3,6-bis(trimethylsilyl)-1,2-benzenedithiolate(2-), and (B)2- = 1,2-bis(4-tert-butylphenyl)ethylene-1,2-dithiolate(2-) and (A*)1- and (B*)1- represent the corresponding monoanionic radicals. Electrochemical and chemical one-electron oxidation of 1 and 2 in CH2Cl2 solution affords the monomeric monocations [PtII(tbpy)(A*)]+ (1a) and [PtII(tbpy)(B*)]+ (2a), both of which possess an S = 1/2 ground state. The corresponding spin doublet monocationic dimers [PtII2(tbpy)2(A)(A*)]+ (1b) and [PtII2(tbpy)2(B)(B*)]+ (2b) were electrochemically generated in solution (50% oxidation) and identified by X-band EPR spectroscopy. Complete one-electron oxidation of 1 and 2 yielded the diamagnetic dimers [PtII2(tbpy)2(A*)2]2+ (1c) and [PtII2(tbpy)2(B*)2]2+ (2c) which are in equilibrium with the corresponding paramagnetic monomers 1a and 2a in solution. The crystal structure of [PtII2(tbpy)2(B*)2](PF6)2.3CH2Cl2 (2c) revealed a centrosymmetric, lateral dimer whose bridging part is a PtII2(mu2-S)2 rhomb; the metal ions possess a square based pyramidal geometry. Solid-state sulfur K-edge X-ray absorption spectra of 1, 2, 2a, 2c, and [PtII(B*)2]0 (4) have been recorded, which clearly show that a sulfur-centered radical (B*)1- is present in 2a, 2c, and 4. The absence of ligand-based radicals in 1 and 2 is also clearly established. One-electron oxidation of [Pt(PPh3)2(B)] (3) afforded only the spin doublet species [PtII(PPh3)2(B*)]+ (3a); no dimer formation was detected. Synthesis and crystal structure of square planar [PtII(B*)2]0.thf are also reported.

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Self-sensitized photo-oxidation of platinum(II) complexes of 1,10-phenanthroline with 3,4-dimercaptotoluene and thiosalicylic acid by 1O2

Cited by 13 publications

References 12 publications

Tuning the Excited-State Properties of Platinum(II) Diimine Dithiolate Complexes

Tuning the Excited-State Properties of Platinum(II) Diimine Dithiolate Complexes

Photooxidation of Diimine Dithiolate Platinium(II) Complexes Induced by Charge Transfer to Diimine Excitation

Dimerization Processes of Square Planar [Pt^II(^tbpy)(dithiolato^•)]⁺ Radicals

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Self-sensitized photo-oxidation of platinum(II) complexes of 1,10-phenanthroline with 3,4-dimercaptotoluene and thiosalicylic acid by 1O2

Cited by 13 publications

References 12 publications

Tuning the Excited-State Properties of Platinum(II) Diimine Dithiolate Complexes

Tuning the Excited-State Properties of Platinum(II) Diimine Dithiolate Complexes

Photooxidation of Diimine Dithiolate Platinium(II) Complexes Induced by Charge Transfer to Diimine Excitation

Dimerization Processes of Square Planar [PtII(tbpy)(dithiolato•)]+ Radicals

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Dimerization Processes of Square Planar [Pt^II(^tbpy)(dithiolato^•)]⁺ Radicals