Molecular Design Principles for Photoactive Transition Metal Complexes: A Guide for “Photo-Motivated” Chemists

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: March 27, 2025

Luminescence and photochemistry involve electronically excited states that are inherently unstable therefore spontaneously decay to electronic ground states, in most cases by nonradiative energy release generates heat. This dissipation can occur on a time scale of 100 fs (∼10–13 s) usually needs be slowed down at least the nanosecond (∼10–9 for luminescence intermolecular occur. is challenging task with many different factors consider. An alternative emerging strategy target dissociative lead metal–ligand bond homolysis subnanosecond access synthetically useful radicals. Based thorough review recent advances field, this article aims provide concise guide obtaining luminescent photochemically coordination compounds d-block elements. We hope encourage "photo-motivated" chemists who have been reluctant apply their synthetic other knowledge photophysics photochemistry, we intend stimulate new approaches control state behavior.

Language: Английский

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Unraveling the Roles of Amines in Atom Transfer Radical Polymerization in the Dark

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: April 2, 2025

Multidentate amines have been widely used as ligands (L) for Cu-catalysts in atom transfer radical polymerization (ATRP) and electron donors photochemically induced polymerizations. However, mechanistic aspects of the role ATRP dark remained elusive. Herein, structure-activity relationship related reactions with Br-CuII/L complexes and/or alkyl bromides (R-Br) were investigated 25 amines. Amines function reducing agents via an outer sphere (OSET) mechanism, enabling slow but continuous generation CuI/L activators inducing controlled ATRP. two amines, diazabicyclo(5.4.0)undec-7-ene (DBU) 1,1,3,3-tetramethylguanidine (TMG), reduced faster, suggesting inner (ISET) process. ATRP, starting initial deactivators (Br-CuII/L) species, proceeded presence excess tertiary such tris[2-(dimethylamino)ethyl]amine (Me6TREN), 1,4-diazabicyclo[2.2.2]octane (DABCO), TMG at room temperature afforded polymers low dispersities (Đ ≤ 1.15). With copper(II) triflate complex (CuII/L+2, -(OTf)2), which has a more positive reduction potential, several inexpensive secondary including triethylamine (TEA) dimethylethanolamine (DMAE). Interestingly, multidentate also served direct R-Br elevated temperatures (60 °C). In all cases, chains initiated not by amine cations byproducts transfer. enabled residual air flasks large headspace, underpinning them robust accessible agent practical applications.

Language: Английский

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Cyclometallated Co(III) Complexes with Lowest-Energy Charge Transfer Excited States Accessible with Visible Light

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: April 10, 2025

The Co(III) complexes, cis-[Co(ppy)2(L)]PF6, where ppy = 2-phenylpyridine and L bpy (2,2'-bipyridine; 1), phen (1,10-phenanthroline; 2), DAP (1,12-diazaperylene; 3), are reported their photophysical properties were investigated to evaluate potential as sensitizers for applications that include solar energy conversion schemes photoredox catalysis. Calculations show cyclometallation in the cis-[Co(ppy)2(L)]PF6 series affords strong Co(dπ)/ppy(π) orbital interactions result a Co/ppy(π*) highest occupied molecular (HOMO) lowest unoccupied (LUMO) localized on diimine ligand, L(π*). Complexes 1-3 exhibit relatively invariant oxidation potentials, whereas reduction event is dependent identity of L, consistent with theoretical predictions. For 3 broad → L(π*) metal/ligand-to-ligand charge transfer (ML-LCT) absorption band observed CH3CN maxima at 507 nm, extending beyond 600 nm. Upon excitation 1ML-LCT transition, transient features population 3ML-LCT excited state lifetimes, τ, 3.0 ps, 4.6 42 ps 1, 2 respectively observed. irradiation 505 able reduce methyl viologen (MV2+), an electron acceptor commonly photocatalytic schemes. To our knowledge, represents first heteroleptic complex combines ligand lowest-lying metal-to-ligand states undergo photoinduced low-energy green light. As such, structural design important step toward d6 photosensitizers based earth abundant metals.

Language: Английский

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Synergistic LMCT and Ni Catalysis for Methylative Cross-Coupling Using tert-Butanol: Modulating Radical Pathways via Selective Bond Homolysis

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: April 18, 2025

Ligand-to-metal charge transfer (LMCT) excitation has emerged as a potent strategy for the selective generation of heteroatom-centered radicals, yet its full potential in modulating open-shell radical pathways remains underexplored. Here, we present photocatalytic methylative cross-coupling reaction that capitalizes on synergistic interplay between LMCT and Ni catalysis, enabling use tert-butanol an efficient benign methylating reagent. The electron-deficient ligand 2,6-ditrifluoromethyl benzoate facilitates Ce(IV)-mediated bond scission tert-butanol, generating methyl is subsequently captured by catalytic cycle to form C-CH3 bonds. Under mild conditions, this affords methylation sp3 carbons adjacent carbonyls sp2 centers, demonstrating broad functional group tolerance applicability late-stage functionalization bioactive molecules. Additionally, trideuteromethylative coupling can be facilely achieved using commercial tert-butanol-d10. This approach circumvents need traditional tert-butoxy precursors, such peroxides, while strategically pathway favor β-scission suppress unwanted formation solution. Mechanistic studies reveal plays crucial role facilitating generation, supporting concerted Ce-OR β-C-C homolysis mechanism, further evidenced modulation regioselectivity alkoxy radical-mediated β-scission.

Language: Английский

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Extend of Ligand‐Metal Charge Transfer (LMCT) Deciding Multi‐Responsive Colourimetric Sensing of Mn(II)/Mn(III)/Pb(II) by a Squaramide Ligand

ChemistrySelect, Journal Year: 2025, Volume and Issue: 10(17)

Published: April 28, 2025

Abstract Manganese sensing using ligands remains challenging due to the stability of manganese complexes and disproportionation reactions in solvents. Herein, we report colourimetry‐based fast reliable differential Mn(II), Mn(III), squaramide‐ligands with pyridine functionality colourimetrically. The efficiency these is contingent on disposition nitrogen relative squaramide ring sustained by presence acetate ions. electronic 1 H‐NMR measurements depict complexation metal ion ligand molecules. In contrast, electron paramagnetic resonance (EPR) suggest that extent ligand‐to‐metal charge transfer (LMCT) primarily responsible for Mn(II) Mn(III) different colours. also produces selective chromogenic responses Pb(II) limit detection (LOD) ions ≈52 n 84 nM, respectively, where LOD 17.9 n. Visually, response below 10 µ concentration filter paper as low < can be easily sensed, which used portable strips real‐life samples.

Language: Английский

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