Sledesky Jack M, Zimmerman John H, London Henry C, Lambert Ethan C, McMillen Colin D, Barker Matilda, Hanson Kenneth, Wagenknecht Paul S
Department of Chemistry, Furman University, Greenville, South Carolina 29609, United States.
Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States.
Inorg Chem. 2025 Jul 28;64(29):14977-14988. doi: 10.1021/acs.inorgchem.5c01773. Epub 2025 Jul 17.
Coordination complexes containing d metals with long-lived ligand-to-metal charge transfer (LMCT) excited states are promising candidates for use as photosensitizers. Previously, CpTi(CPh)CuBr (where Cp = pentamethylcyclopentadienyl and CPh = phenylethynyl) was reported to be emissive in THF solution at room temperature (RT) from an excited state with significant Cp*-to-Ti LMCT character (λ = 693 nm, τ = 0.18 μs). However, the corresponding cyclopentadienyl complex was not emissive. Structural constraint was hypothesized as a reason for the enhanced photophysics of the Cp* complex. To further test this hypothesis, the corresponding complex with -xylylethynyl ligands, CpTi(CPhMe)CuBr, has been prepared and characterized. X-ray crystallography demonstrates significant steric congestion caused by the additional methyl substituents. This xylylethynyl complex is emissive in THF solution at RT and the lifetime is approximately 10-fold greater (λ = 734 nm, τ = 1.6 μs) than the corresponding phenylethynyl complex. Spectroscopic and computational data are consistent with this emission being phosphorescence with significant Cp-to-Ti and xylylethynyl-to-Ti LMCT character. The evidence is also consistent with an excited state that is less distorted for the xylylethynyl complex than the phenylethynyl complex. The sterically induced, long lifetime of the xylylethynyl complex enabled its use in photon upconversion and O formation.
含有具有长寿命配体到金属电荷转移（LMCT）激发态的d金属的配位络合物是有潜力用作光敏剂的候选物。此前有报道称，CpTi(CPh)CuBr（其中Cp = 五甲基环戊二烯基，CPh = 苯乙炔基）在室温（RT）下于四氢呋喃（THF）溶液中从具有显著Cp到Ti的LMCT特征的激发态发射（λ = 693 nm，τ = 0.18 μs）。然而，相应的环戊二烯基络合物不发光。结构限制被假定为Cp络合物光物理性质增强的一个原因。为了进一步验证这一假设，制备并表征了具有 - 二甲苯乙炔基配体的相应络合物CpTi(CPhMe)CuBr。X射线晶体学表明额外的甲基取代基导致了显著的空间拥挤。这种二甲苯乙炔基络合物在室温下于四氢呋喃溶液中发光，其寿命比相应的苯乙炔基络合物大约长10倍（λ = 734 nm，τ = 1.6 μs）。光谱和计算数据与这种发射是具有显著Cp到Ti和二甲苯乙炔基到Ti的LMCT特征的磷光一致。证据还表明，二甲苯乙炔基络合物的激发态比苯乙炔基络合物的激发态扭曲程度更小。二甲苯乙炔基络合物的空间诱导长寿命使其能够用于光子上转换和氧生成。
