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Keywords:

  • Enzyme models;
  • Metalloenzymes;
  • Hydrogenases;
  • Iron;
  • Sulfur;
  • Subphthalocyanine

Abstract

The first two model compounds for [FeFe]-hydrogenases that contain a subphthalocyanine (SubPc) macrocycle, namely, [{(μ-SCH2)2N(CH2)2CO2-3-C6H4S2C6H4-3′-O(SubPc)}Fe2(CO)6] (5) and [{(μ-SCH2)2NC6H4-4-O(SubPc)}Fe2(CO)6] (8), have been synthesized and structurally characterized. The treatment of chlorosubphthalocyanine (SubPc-Cl, 1) with (3-HOC6H4S)2 in toluene gave the corresponding phenoxy-substituted SubPc derivative 3-HOC6H4S2C6H4-3′-O(SubPc) (2) in 78 % yield, whereas the reaction of in-situ-generated [(μ-HOCH2S)2Fe2(CO)6] (3) with β-alanine afforded diiron complex [{(μ-CH2S)2N(CH2)2CO2H}Fe2(CO)6] (4) in 53 % yield. Further treatment of 2 with 4 in the presence of N,N′-dicyclocarbodiimide (DCC) and N,N-dimethyl-4-aminopyridine (DMAP) in CH2Cl2 resulted in the formation of model compound 5 in 86 % yield. Model compound 8 could be prepared by two methods. One method involves the reaction of in-situ-generated 3 with 4-aminophenol in tetrahydrofuran (THF) to give diiron complex [{(μ-CH2S)2NC6H4OH-4}Fe2(CO)6] (6) in 61 % yield and further treatment of SubPc-Cl (1) with 6 in toluene to give 8 in 13 % yield. The other method involves the reaction of SubPc-Cl (1) with silver triflate (AgOTf) followed by treatment of the resulting intermediate SubPc-OTf (7) with 6 in the presence of Et3N to produce 8 in a much higher yield (59 %). All the new precursors (2, 4, and 6) and the model compounds 5 and 8 have been fully characterized by elemental analysis and various spectroscopy techniques, as well by X-ray crystallography for 2, 4, 6, and 8. In addition, the photoinduced H2 production catalyzed by model 8 was preliminarily investigated.