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13C or Not 13C: selective synthesis of asymmetric carbon-13-labeled platinum(II) cis-acetylides.Archer, Stuart A.; Keane, Theo; Delor, Milan; Meijer, Anthony J. H. M.; Weinstein, Julia A.; University of Sheffield; Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom; Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom; Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom; Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom; et al. (American Chemical Society, 2016-08-09)Asymmetric isotopic labeling of parallel and identical electron- or energy-transfer pathways in symmetrical molecular assemblies is an extremely challenging task owing to the inherent lack of isotopic selectivity in conventional synthetic methods. Yet, it would be a highly valuable tool in the study and control of complex light-matter interactions in molecular systems by exclusively and nonintrusively labeling one of otherwise identical reaction pathways, potentially directing charge and energy transport along a chosen path. Here we describe the first selective synthetic route to asymmetrically labeled organometallic compounds, on the example of charge-transfer platinum(II) cis-acetylide complexes. We demonstrate the selective 13C labeling of one of two acetylide groups. We further show that such isotopic labeling successfully decouples the two ν(C≡C) in the mid-IR region, permitting independent spectroscopic monitoring of two otherwise identical electron-transfer pathways, along the 12C≡12C and 13C≡13C coordinates. Quantum-mechanical mixing leads to intriguing complex features in the vibrational spectra of such species, which we successfully model by full-dimensional anharmonically corrected DFT calculations, despite the large size of these systems. The synthetic route developed and demonstrated herein should lead to a great diversity of asymmetric organometallic complexes inaccessible otherwise, opening up a plethora of opportunities to advance the fundamental understanding and control of light-matter interactions in molecular systems.