McCullough Bradley J, Neyhouse Bertrand J, Schrage Briana R, Reed Demi T, Osinski Allen J, Ziegler Christopher J, White Travis A
Department of Chemistry and Biochemistry, Clippinger Laboratories , Ohio University , Athens , Ohio 45701 , United States.
Department of Chemistry, Knight Chemical Laboratory , University of Akron , Akron , Ohio 44325 , United States.
Inorg Chem. 2018 Mar 5;57(5):2865-2875. doi: 10.1021/acs.inorgchem.7b03273. Epub 2018 Feb 15.
The synthesis of two new heteroleptic Cu(I) photosensitizers (PS), [Cu(Xantphos)(NN)]PF (NN = biq = 2,2'-biquinoline, dmebiq = 2,2'-biquinoline-4,4'-dimethyl ester; Xantphos = 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene), along with the associated structural, photophysical, and electrochemical properties, are described. The biquinoline diimine ligand extends the PS light absorbing properties into the visible with a maximum absorption at 455 and 505 nm for NN = biq and dmebiq, respectively, in CHCl solvent. Following photoexcitation, both Cu(I) PS are emissive at low energy, albeit displaying stark differences in their excited state lifetimes (τ = 410 ± 5 (biq) and 44 ± 4 ns (dmebiq)). Cyclic voltammetry indicates a Cu-based HOMO and NN-based LUMO for both complexes, whereby the methyl ester substituents stabilize the LUMO within [Cu(Xantphos)(dmebiq)] by ∼0.37 V compared to the unsubstituted analogue. When combined with HO, N,N-dimethylaniline (DMA) electron donor, and cis-[Rh(NN)Cl]PF (NN = Mebpy = 4,4'-dimethyl-2,2'-bipyridine, bpy = 2,2'-bipyridine, dmebpy = 2,2'-bipyridine-4,4'-dimethyl ester) water reduction catalysts (WRC), photocatalytic H evolution is only observed using the [Cu(Xantphos)(biq)] PS. Furthermore, the choice of cis-[Rh(NN)Cl] WRC strongly affects the catalytic activity with turnover numbers (TON = mol H per mol Rh catalyst) of 25 ± 3, 22 ± 1, and 43 ± 3 for NN = Mebpy, bpy, and dmebpy, respectively. This work illustrates how ligand modification to carefully tune the PS light absorbing, excited state, and redox-active properties, along with the WRC redox potentials, can have a profound impact on the photoinduced intermolecular electron transfer between components and the subsequent catalytic activity.
描述了两种新型杂配铜（I）光敏剂（PS），即[Cu（Xantphos）（NN）]PF（NN = biq = 2,2'-联喹啉，dmebiq = 2,2'-联喹啉-4,4'-二甲酯；Xantphos = 4,5-双（二苯基膦基）-9,9-二甲基氧杂蒽）的合成及其相关的结构、光物理和电化学性质。在CHCl₃溶剂中，联喹啉二亚胺配体将PS的光吸收性能扩展到可见光区域，对于NN = biq和dmebiq，最大吸收波长分别在455和505 nm处。光激发后，两种铜（I）PS在低能量下均有发射，尽管它们的激发态寿命存在显著差异（τ = 410 ± 5（biq）和44 ± 4 ns（dmebiq））。循环伏安法表明两种配合物均以铜为HOMO，以NN为LUMO，与未取代的类似物相比，甲酯取代基使[Cu（Xantphos）（dmebiq）]中的LUMO稳定了约0.37 V。当与HO、N，N-二甲基苯胺（DMA）电子供体和顺式-[Rh（NN）Cl]PF（NN = Mebpy = 4,4'-二甲基-2,2'-联吡啶，bpy = 2,2'-联吡啶，dmebpy = 2,2'-联吡啶-4,4'-二甲酯）析氢催化剂（WRC）组合时，仅使用[Cu（Xantphos）（biq）]PS观察到光催化析氢。此外，顺式-[Rh（NN）Cl]WRC的选择对催化活性有很大影响，对于NN = Mebpy、bpy和dmebpy，周转数（TON = 每摩尔铑催化剂产生的氢气摩尔数）分别为25 ± 3、22 ± 1和43 ± 3。这项工作说明了如何通过配体修饰来精细调节PS的光吸收、激发态和氧化还原活性性质，以及WRC的氧化还原电位，这对组分之间的光诱导分子间电子转移和随后的催化活性会产生深远影响。
