¹³C or Not ¹³C: Selective Synthesis of Asymmetric Carbon-13-Labeled Platinum(II) cis-Acetylides

Abstract

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 (13)C 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 (12)C≡(12)C and (13)C≡(13)C 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.

Directing the path of light-induced electron transfer at a molecular fork using vibrational excitation

“…24 We confirmed that the excited state behaviour of 1* is not affected by isotopic labelling, and is identical to that of the symmetric fully labelled 13 1, and of the unlabelled 1 (see Supplementary Fig. 1-3 for transient absorption data, Supplementary Fig.…”

“…Analysis of the calculated fully-anharmonically corrected vibrations of the molecule shows that the observed doublet is due to a combination band of two vibrations localized on the 13 C-arm of the molecule in resonance with the ν( 13 C) fundamental, leading to quantum mechanical mixing and intensity borrowing between the two modes. 24,25 A prerequisite to ensure that mode-selective excitation with an IR pump leads to localised excitations on either arm of the molecule is that ν( 13 C) and ν( 12 C) are decoupled. To ascertain that this condition is fulfilled, two-dimensional IR experiments (2DIR), which can be used to probe off-diagonal coupling elements between sets of vibrations, 26 were performed on this system.…”

Platinum(II)-Substituted Phenylacetylide Complexes Supported by Acyclic Diaminocarbene Ligands

“…Platinum acetylide complexes, oligomers, and polymers are attractive in photochemical and optoelectronic applications such as in organic light emitting diodes, optical limiting materials, photovoltaic devices, photocatalysis, and stimuli-responsive materials, owing to their rich photophysical properties. − These excellent photophysical properties are attributed to the interaction of the large spin–orbit coupling of platinum with the acetylide ligands through orbital overlap. , As a result, intersystem crossing from the singlet to triplet excited state of the platinum complex is enhanced and thus improves the phosphorescence efficiency. In the broader optoelectronic field, the development of green and red phosphorescent emitters has progressed to the point of commercial devices.…”

A theoretical study on the second-order nonlinear optical properties of Pt(ii) bis-acetylide complexes: substituent and redox effects

“…Molecular, oligomeric, and polymeric Pt(II) acetylides have garnered widespread interest due to their structural diversity, rich photophysical properties, and potential use in photochemical and optoelectronic fields. [38][39][40][41][42][43]…”

“…Molecular, oligomeric, and polymeric Pt( ii ) acetylides have garnered widespread interest due to their structural diversity, rich photophysical properties, and potential use in photochemical and optoelectronic fields. 38–43 Wu et al synthesized a new type of four-coordinate Pt( ii ) bis-acetylide chromophores with the formula cis -[(Pt(CN t Bu))(ADC)(CCR) 2 ](R = –Ph), where CCR is an acetylide, CN t Bu is a tert -butyl-isocyanide, and ADC is an acyclic diaminocarbene, as shown in Fig. 1 (named complex 1 ).…”