Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
Inorg Chem. 2010 Jan 4;49(1):29-37. doi: 10.1021/ic9008015.
Comparative studies of axial CO and solvent coordination to iron(II) protoporphyrin IX (FeIIPPIX) anchored to the surface of mesoporous nanocrystalline (anatase) TiO2 thin films (FeIIPPIX/TiO2) immersed in dimethyl sulfoxide (DMSO), pyridine (py), and methanol (MeOH) and to FeIIPPIX in fluid DMSO and py solution are reported. The equilibrium constants, KeqCOS, for CO coordination to FeIIPPIX/TiO2 immersed in py (2.4 x 10(3) M-1) < DMSO (6 x 10(4) M-1) < MeOH (2.3 x 10(5) M-1) were quantified. The corresponding values in fluid py or DMSO solution were 2 times larger (4.5 x 10(3) and 1 x 10(5) M-1, respectively). The observed ligand exchange rates (kobs) measured after pulsed 532 nm laser excitation (5-6 ns fwhm, 1-3 mJ/pulse) of (S)(CO)FeIIPPIX/TiO2, where S is solvent, in saturated CO solutions were measured: py (2.2 s-1), DMSO (460 s-1), MeOH (2.09 x 10(5) s-1). The corresponding values in fluid solution were 2.0 s-1 (py) and 230 s-1 (DMSO). The observed ligand exchange rate varied linearly with [CO], and second-order rate constants were determined for FeIIPPIX/TiO2 immersed in DMSO (3.1 x 10(5) M-1 s-1) and MeOH (1.5 x 10(7) M-1 s-1). The observed rate for CO addition to (py)2FeIIPPIX/TiO2 immersed in py did not vary linearly with [CO]. The relevance of the measured kinetics and thermodynamics to a dissociative mechanism for ligand exchange is discussed.
报道了将轴向 CO 和溶剂配位到介孔纳米晶（锐钛矿）TiO2 薄膜表面固定的原卟啉 IX 铁(II)（FeIIPPIX/TiO2）的比较研究，这些薄膜分别浸入二甲亚砜（DMSO）、吡啶（py）和甲醇（MeOH）以及 FeIIPPIX 在 DMSO 和 py 溶液中的流体。定量了 CO 与浸入 py（2.4 x 10(3) M-1）<DMSO（6 x 10(4) M-1）<MeOH（2.3 x 10(5) M-1）中的 FeIIPPIX/TiO2 配位的平衡常数 KeqCOS。在流体 py 或 DMSO 溶液中的相应值大 2 倍（分别为 4.5 x 10(3) 和 1 x 10(5) M-1）。在饱和 CO 溶液中用 532nm 激光脉冲（5-6ns 半峰全宽，1-3mJ/脉冲）激发（S）（CO）FeIIPPIX/TiO2 后测量的观察到的配体交换速率（kobs），其中 S 是溶剂，在饱和 CO 溶液中的测量值为：py（2.2 s-1）、DMSO（460 s-1）、MeOH（2.09 x 10(5) s-1）。在流体溶液中的相应值为 2.0 s-1（py）和 230 s-1（DMSO）。观察到的配体交换速率与 [CO] 呈线性关系，并确定了 FeIIPPIX/TiO2 浸入 DMSO（3.1 x 10(5) M-1 s-1）和 MeOH（1.5 x 10(7) M-1 s-1）中的二级速率常数。在 py 中浸入（py）2FeIIPPIX/TiO2 的 CO 加成到（py）2FeIIPPIX/TiO2 的观察到的速率不随 [CO] 线性变化。讨论了测量的动力学和热力学与配体交换的离解机制的相关性。
