Impact of the Synergistic Collaboration of Oligothiophene Bridges and Ruthenium Complexes on the Optical Properties of Dumbbell‐Shaped Compounds |
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| Authors: | Dr Rubén D Costa Dr Juan Aragó Prof Dr Enrique Ortí Dr Ted M Pappenfus Prof Dr Kent R Mann Dr Katarzyna Matczyszyn Prof Dr Marek Samoc Dr José L Zafra Prof Dr Juan T López Navarrete Prof Dr Juan Casado |
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| Institution: | 1. Instituto de Ciencia Molecular, Universidad de Valencia, 46980 Paterna, Valencia (Spain);2. Friedrich‐Alexander‐Universit?t Erlangen‐Nürnberg, Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular, Materials (ICMM), 91058, Erlangen (Germany);3. Division of Science and Mathematics, University of Minnesota, Morris, MN 56267 (USA);4. Department of Chemistry, University of Minnesota, Minneapolis, MN 55455 (USA);5. Institute of Physical and Theoretical Chemistry, Wroclaw University of Technology, 50370 Wroclaw (Poland);6. Department of Physical Chemistry, University of Málaga, 29071 Málaga (Spain) |
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| Abstract: | The linear and non‐linear optical properties of a family of dumbbell‐shaped dinuclear complexes, in which an oligothiophene chain with various numbers of rings (1, 3, and 6) acts as a bridge between two homoleptic tris(2,2′‐bipyridine)ruthenium(II) complexes, have been fully investigated by using a range of spectroscopic techniques (absorption and luminescence, transient absorption, Raman, and non‐linear absorption), together with density functional theory calculations. Our results shed light on the impact of the synergistic collaboration between the electronic structures of the two chemical moieties on the optical properties of these materials. Experiments on the linear optical properties of these compounds indicated that the length of the oligothiophene bridge was critical for luminescent behavior. Indeed, no emission was detected for compounds with long oligothiophene bridges (compounds 3 and 4 , with 3 and 6 thiophene rings, respectively), owing to the presence of the 3π? π* state of the conjugated bridge below the 3MLCT‐emitting states of the end‐capping RuII complexes. In contrast, the compound with the shortest bridge ( 2 , one thiophene ring) shows excellent photophysical features. Non‐linear optical experiments showed that the investigated compounds were strong non‐linear absorbers in wide energy ranges. Indeed, their non‐linear absorption was augmented upon increasing the length of the oligothiophene bridge. In particular, the compound with the longest oligothiophene bridge not only showed strong two‐photon absorption (TPA) but also noteworthy three‐photon‐absorption behavior, with a cross‐section value of 4×10?78 cm6 s2 at 1450 nm. This characteristic was complemented by the strong excited‐state absorption (ESA) that was observed for compounds 3 and 4 . As a matter of fact, the overlap between the non‐linear absorption and ESA establishes compounds 3 and 4 as good candidates for optical‐power‐limiting applications. |
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| Keywords: | bridging ligands density functional calculations dinuclear ruthenium complexes oligothiophenes Raman spectroscopy ruthenium |
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