Structure and Ultrafast Dynamics of the Charge-Transfer Excited State and Redox Activity of the Ground State of Mono- and Binuclear Platinum(II) Diimine Catecholate and Bis-catecholate Complexes: A Transient Absorption, TRIR, DFT, and Electrochemical Study
Structure and Ultrafast Dynamics of the Charge-Transfer Excited State and Redox Activity of the Ground State of Mono- and Binuclear Platinum(II) Diimine Catecholate and Bis-catecholate Complexes: A Transient Absorption, TRIR, DFT, and Electrochemical Study
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DOI：
10.1021/ic101344t
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发表时间：
2010-11-01
影响因子：
4.6
通讯作者：
Weinstein, Julia A.
中科院分区：
文献类型：
--
作者：
Best, Jonathan;Sazanovich, Igor V.;Weinstein, Julia A.
一系列单核配合物的类型[Pt(布鲁里溃疡(2)猫)4,4’-R-2-bipy)] [Bu2cat 3的二阶阴离子,5-Bu-t(2)儿茶酚和R = H,里,或C (O) NEt2]和类似的双核的复合物基于“背靠背”bis-catechol配体3,3 ',4,4’-tetrahydroxybiphenyl详细研究了地面和激发态通过一系列物理方法包括电化学、UV / vis /近红外线、红外光谱、电子顺磁共振spectro-electrochemistry,时间分辨红外光谱（TRIR）和瞬态吸收光谱（TA）。密度泛函理论计算已被用于支持这些研究，这些研究提供了这些复合物的基态和激发态电子结构以及激发态动力学的详细图像。值得注意的是：(1)首次用TRIR光谱研究了这些发色团的最低能量儿茶酚酸- b>联吡啶（bpy）配体-配体电荷转移（LL’ct）激发态，显示出与bpy自由基阴离子和半醌类相关的一系列瞬态带，以及发生在数百皮秒内的背电子转移；（ii）双核配合物的桥接配体中两个儿茶酚酸单元之间的强电子耦合导致桥接配体的单电子氧化形成离域的平面（3类）“混价”儿茶酚酸2(-)/半醌（近似等于）态；（iii）在双核配合物的LL'CT激发态下，桥接配体是对称的且离域的，而bpy自由基阴离子则定位在配合物的一端。本研究是研究铂（II）儿茶酚酸配合物激发态行为的第一个例子，使用皮秒TRIR和飞秒TA光谱进行。
A series of mononuclear complexes of the type [Pt(Bu(2)cat)(4,4'-R-2-bipy)] [where Bu2cat is the dianion of 3,5-Bu-t(2)-catechol and R = H, Bu-t, or C(O)NEt2] and analogous dinuclear complexes based on the "back-to-back" bis-catechol ligand 3,3',4,4'-tetrahydroxybiphenyl have been studied in detail in both their ground and excited states by a range of physical methods including electrochemistry, UV/vis/near-IR, IR, and electron paramagnetic resonance spectro-electrochemistry, and time-resolved IR (TRIR) and transient absorption (TA) spectroscopy. Density functional theory calculations have been performed to support these studies, which provide a detailed picture of the ground- and excited-state electronic structures, and excited-state dynamics, of these complexes. Notable observations include the following: (i) for the first time, the lowest-energy catecholate -> bipyridine (bpy) ligand-to-ligand charge-transfer (LL'CT) excited states of these chromophores have been studied by TRIR spectroscopy, showing a range of transient bands associated with the bpy radical anion and semiquinone species, and back-electron-transfer occurring in hundreds of picoseconds; (ii) strong electronic coupling between the two catecholate units in the bridging ligand of the dinuclear complexes results in a delocalized, planar (class 3) "mixed-valence" catecholate2(-)/semiquinone(is approximately equal to) state formed by one-electron oxidation of the bridging ligand; (iii) in the LL'CT excited state of the dinuclear complexes, the bridging ligand is symmetrical and delocalized, whereas the bpy radical anion is localized at one terminus of the complex. This study is the first example of an investigation of excited-state behavior in platinum(II) catecholate complexes, performed with the use of picosecond TRIR and femtosecond TA spectroscopy.