摘要
合成了以三联吡啶锇Os(II)配合物为光敏剂的PS-Fe2S2型模拟铁氢化酶分子光催化剂1a及其分子间光催化模型化合物1b和2,研究了配合物1a和1b的吸收光谱,发光光谱及电化学性质.配合物1a和1b均表现出三联吡啶锇Os(II)配合物的MLCT吸收峰;与不含Fe2S2基团的配合物1b相比,在配合物1a中三联吡啶锇Os(II)配合物单元的发光被明显猝灭,猝灭程度为92%.而在同样浓度下,配合物1b与2组成的分子间体系中三联吡啶锇Os(II)配合物的发光仅被猝灭了4%.通过Rehm-Weller方程计算得出由三联吡啶锇Os(II)配合物单元到Fe2S2活性中心的光致电子转移自由能为正,表明分子内1a和分子间1b+2体系均不能发生光致电子转移,体系发光猝灭的原因是三联吡啶锇Os(II)配合物3MLCT激发态与铁氢化酶模拟活性中心Fe2S2的能量转移.
To mimic [FeFe] hydrogenase in nature,a PS-Fe2S2 type molecular dyad 1a and corresponding intermolecular model compounds 1b and 2 were synthesized and characterized.In the case of 1a,bis-terpyridine osmium（Ⅱ） complex as photosensitizer（PS） is covalently linked to a Fe2S2 cluster of [FeFe] hydrogenase mimic active site by a cyanide group.UV-Vis absorption spectrum revealed that both compounds 1a and 1b show two LC absorptions at the range of 280～330 nm,and ^1MLCT absorption at ca.498 nm.Particularly,^3MLCT absorption at 669 nm was clearly observed in compound 1b.Redox property of 1a and 1b was studied by cyclic voltammetry.Compound 1b shows two reduction potentials E（Os^＋2/＋1） and E（Os^＋1/0） at -1.60 and -1.87 eV,and one oxidation potential E（Os%＋2/＋3） at 0.51 eV.As compared with 1b,1a shifts to more negative reduction potentials E（Os%＋2/＋1） and E（Os%＋1/0） at-1.63 and-1.91 eV,respectively,but to more positive oxidation potential E（Os%＋2/＋3） at 0.58 eV.Compound 1a also show an irreversible reduction potential of Fe%1Fe^1→Fe^1Fe^0 at -1.77 eV,which shifts 180 mV more negative than the corresponding reduction potential of compound 2.Excitation of the MLCT absorption of compound 1b leads to a strong luminescence at 740 nm with lifetime of 105 ns in CH3CN.However,the luminescence of dyad 1a was significantly quenched with efficiency of 92%.Under the same condition,the luminescence of 1b was slightly quenched by one equivalent of compound 2.The quenching efficiency of 1b was changed from 4% to 65% when the concentration of 2 was increased from 1 to 10 equivalents.According to Rehm-Weller equation,the photoinduced electron transfer from the excited osmium complex to Fe2S2 moiety neither in intramolecular dyad 1a nor in intermolecular（1b＋2） system is feasible for the uphill free energy change.Consequently,the luminescence quenching in intramolecular dyad 1a and intermolecular （1b＋2） system was tentatively attributed to energy transfer from ^3MLCT of osmium complex to Fe2S2cluster.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2012年第22期2306-2310,共5页
Acta Chimica Sinica
基金
国家科技部(Nos.2009CB22008
2013CB834505)
国家自然科学基金(Nos.21090343
21002108
20973189
50973125
91027041)
中国科学院知识创新工程(No.KGCX2-EW-311-1)资助~~
关键词
铁氢化酶
三联吡啶锇
电子转移
能量转移
[FeFe] hydrogenase
osmium（Ⅱ） bis-terpyridine complex
electron transfer
energy transfer
