Dinitrosyl iron complexes (DNICs) acting as catalyst for photocatalytic hydrogen evolution reaction (HER)

Electrochemical study of {Fe(NO)(2)}(10) DNIC [(2-AMP)Fe(NO)(2)] (1) (2-AMP = 2-aminomethylpyridine) in CH3CN/Na2SO4 aqueous solution (1 M) revealing reversible one-electron redox couples implicated that DNIC 1 may facilitate versatile chemical reactions associated with two-electron HER (hydrogen evolution reaction) processes. The three-component photocatalytic HER system is composed of MeOH-H2O solution (1:1 volume ratio, pH = 11.0) of molecular catalyst DNIC 1 (1.6 mu M), photosensitizer fluorescein (Fl) (1.5 mM) and sacrificial electron donor triethylamine (0.36 M) was developed. The reductive quenching rate (R-1) (electron transfer from Et3N to Fl) and the oxidative quenching rate (R-2) (electron transfer from [Fl](-) to DNIC 1) were calculated as 2.11 x 10(7) s(-1) and 3.984 x 10(4) s(-1), respectively. The faster electron transfer from [Fl](-) to DNIC 1, compared to the electron-transfer rate (R-3) from [DNIC 1](-) to H2O, rationalized the accumulation of the transient-stable [DNIC 1](-), degrading to [DNIC 1](-)-transformed photocatalytic active particles (Fe3O4 [major]). The three-component photocatalytic system composed of MeOH-H2O solution of the isolated particles (2 mg), Fl (1.5 mM), and Et3N (0.36 M) was also employed for photocatalytic HER reaching TON 13456 mu mol(H2)/g(catalyst), TOF 2691 hr(-1)mu mol(H2)/g(catalyst) and the apparent quantum yield 3.71% under radiation (480 nm). That is, for the photocatalytic HER device constructed via a combination of DNIC 1, Fluorescein, and triethylamine, both the homogeneous catalytic HER triggered by {Fe(NO)(2)}(10)-reduced [DNIC 1](-) and the heterogeneous catalytic HER promoted by [DNIC 1](-)-transformed particles operated concomitantly to drive this photocatalytic HER.