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

TLDR: In this paper, the optical absorption, photoluminescence, and photocurrent action spectra of trans-Pt(PBu3n)2Cl2 with one equivalent of the diterminal alkynyl oligothiophenes H-C≡C-R-C-H in CH2Cl 2/iPr2NH at room temperature were reported.

Abstract: Soluble, rigid-rod organometallic polymers trans-[-Pt(PBu3n)2–C≡C–R–C≡C–]∞ (R=bithienyl 2, terthienyl 3) have been synthesized in good yields by the CuI-catalyzed dehydrohalogenation reaction of trans-[Pt(PBu3n)2Cl2] with one equivalent of the diterminal alkynyl oligothiophenes H–C≡C–R–C≡C–H in CH2Cl2/iPr2NH at room temperature. We report the thermal properties, and the optical absorption, photoluminescence, and photocurrent action spectra of 1 (trans-[–Pt(PBu3n)2–C≡C–R–C≡C–]∞, R=thienyl), 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 T1 triplet excited state is extended over several thiophene ...