Cooperative Redox Regulation of [4Fe-4S] Ferredoxin Model Arenethiolate Complexes by NH···S Hydrogen Bonds and an Aromatic C–H···S Interaction

Abstract

A series of the model complexes containing ortho-substituted arenethiolato ligands, ((Et4N)2[Fe4S4(S-2-RCONHC6H4)4] {R = Ph (1), 4-MeO–C6H4 (2), and 4-F–C6H4 (3)} and (Et4N)2[Fe4S4{S-2,6-(RCONH)2C6H3}4] {R = Ph (4), 4-MeO–C6H4 (5), and 4-F–C6H4 (6)}) was synthesized and characterized by 1H NMR, IR spectroscopy, and cyclic voltammetry. The solution structures of these complexes are discussed based on their 1H NMR T1 data and molecular-dynamics calculations. Complex 4 has a shorter distance (av. 4.3 Å) between the protons of the benzoyl group and the inorganic sulfur atom of the [4Fe-4S] cluster than the corresponding ones of 1 (av. 6.2 Å). These results indicate the C–H···S interaction between the protons of the benzoyl group and the sulfur atom of the [4Fe-4S] cluster. The [Fe4S4(SAr)4]2−/[Fe4S4(SAr)4]3−redox potential for 1 and 4 are −0.86 and −0.65 V, respectively. The difference between 1 and 4 is Δ0.21 V. This is larger than the value Δ0.11 V between [Fe4S4(S-2-t-BuCONHC6H4)4]2− (−0.91 V) and [Fe4S4{S-2,6-(t-BuCONH)2C6H3}4]2− (−0.80 V), considered to be the difference between singly and doubly NH··&middotS hydrogen-bonded complexes. The redox potentials for 1—6 follow the trend of the Hammett σm values, showing that the aromatic ring of the benzoyl group interacts with the [4Fe-4S] cluster directly. A cooperative effect between the C–H···S interaction and the NH···S hydrogen bond is thus found to regulate the redox potential of the model complexes.

Effects of alkylthio groups on phase transitions of organic molecules and liquid crystals: a comparative study with alkyl and alkoxy groups

“…3 Å were observed, implying the weak S⋯HC interactions. [2][3][4][5][6][7][8] On the other hand, the estimated S⋯S distances of the methylthio groups between the neighboring molecules were ca. 4.2, 5.2, and 5.8 Å.…”

“…For example, indicated interatomic contacts have been associated with various interactions, such as S⋯HC (ref. [2][3][4][5][6][7][8] and S⋯π interactions. 9,10 The dispersion forces derived from the sulfur atom likely contribute to increasing the phase transition temperature of organic LC molecules.…”

Synthetic analogs for evaluating the influence of N–H⋯S hydrogen bonds on the formation of thioester in acetyl coenzyme a synthase

“…Ortho - pivaloylaminobenzene disulfide and para -pivaloylaminobenzene disulfide were synthesized from the corresponding amino disulfides and pivaloyl chloride as described previously. 34 (tmeda)NiMe 2 35 and (dppe)NiMe 2 36 were synthesized via a modification of the procedure reported 28 for (dippe)NiMe 2 in which dippe was replaced with tmeda and dppe, respectively. (Py) 4 NiCl 2 28 was prepared via addition of pyridine to a suspension of anhydrous NiCl 2 in ethyl ether.…”

Synthesis and characterization of cyclometallated palladium(II) and platinum(II) complexes with amide-thiolate ligands

“…Bis(2-benzamidophenyl) disulfide (H 2 L-LH 2 ) was synthesized by the modified method reported in [21].…”