Evolution of lowest singlet and triplet excited states with number of thienyl rings in platinum poly-ynes

Abstract

The photophysical behavior of 3-chloro-7-methoxy-4-methylcoumarin related to the energy separation of the two lowest-lying singlet excited states Soluble, rigid-rod organometallic polymers trans-͓-Pt(PBu 3 n ) 2 -CwC-R-CwC-͔ ϱ ͑Rvbithienyl 2, terthienyl 3͒ have been synthesized in good yields by the CuI-catalyzed dehydrohalogenation reaction of trans-͓Pt(PBu 3 n ) 2 Cl 2 ͔ with one equivalent of the diterminal alkynyl oligothiophenes H-CwC-R-CwC-H in CH 2 Cl 2 / i Pr 2 NH at room temperature. We report the thermal properties, and the optical absorption, photoluminescence, and photocurrent action spectra of 1 ͑trans-͓ -Pt(PBu 3 n ) 2 -CwC-R-CwC-͔ ϱ , Rvthienyl͒, 2 and 3 as a function of the number of thiophene rings within the bridging ligand. With increasing thiophene content, the optical gap is reduced and the vibronic structure of the singlet emission changes toward that typical for oligothiophenes. We also find the intersystem crossing from the singlet excited state to the triplet excited state to become reduced, while the singlet-triplet energy gap remains unaltered. The latter implies that, in these systems, the T 1 triplet excited state is extended over several thiophene rings. The photoconducting properties do not depend on the size of the thiophene fragment. We discuss and compare our results with studies on oligothiophenes and related organometallic polymers.

Synthesis, optical and photoconducting properties of platinum poly-yne polymers functionalized with electron-donating and electron-withdrawing bithiazole units

“…As compared to the poly(alkylbithiazoles), the absorption maxima also shifts to longer wavelengths upon incorporation of a heavy transition element in the polymer backbone 4) . We also note that, in energy terms, the optical gap decreases when introducing platinum moieties at the ends of the ligands, and the bandgap of 6 is found to be smaller than that in the analogous platinum polymer with a 2,29-bithiophene-5,59-diyl unit by 0.2 eV 8) .…”

“…In a manner similar to the platinum oligothienyl polymers, we attribute this peak to emission from the singlet excited state (S 1 eS 0 ) due to the small Stokes' shift between the strongest bands in the absorption and the emission spectra of 6 (ca. 0.35 eV) 8) . This assignment is also consistent with the observed temperature dependence of the emission features of 6 (Fig.…”

Chemistry of chromium bis-acetylide complexes

“…The Cr1-C7 and C7-C8 bond distances are 1.951(11) and 1.335(11) Å , respectively. The observed bond angles for C7-Cr1-P1 and P1-Cr1-P2 were 90.3 (9) and 82.64(3)°.…”

Mechanistic Investigations of Organic Aggregates with Different Topologies for Optical Limiting Applications

“…New thiophene-based cyclic light harvesting antenna is of great importance for new generation of thiophene-based efficient photovoltaic systems different spin multiplicity. [49][50][51] Specifically, the platinum atom generates strong spin-orbit coupling (heavy atom effect) allowing for ultra-fast intersystem crossing (ISC) or, in the opposite route, the ability for singlet and triplet electron-hole pairs to recombine emissively. Furthermore, the platinum d-orbitals conjugated with the ligand π-orbitals allow for charge migration across the oligomers.…”