Reaction of [Fe(N-Et-HPTB)(CHCOS)](BF) (1) with (NO)(BF) produces a nonheme mononitrosyl diiron(II) complex, [Fe(N-Et-HPTB)(NO)(DMF)](BF) (2). Complex 2 is the first example of a [Fe{Fe(NO)}] species and is also the first example of a mononitrosyl diiron(II) complex that mediates the reduction of NO to NO. This work describes the selective synthesis, detailed characterization and NO reduction activity of 2 and thus provides new insights regarding the mechanism of flavodiiron nitric oxide reductases.

Desulfurization of organosulfur compounds is a highly important reaction because of its relevance to the hydrodesulfurization (HDS) process of fossil fuels. A reaction system involving Co(BF)·6HO and the dinucleating ligands HBPMP or HPhBIMP has been developed that could desulfurize a large number of thiophenes, sulfides, and thiols to generate the complexes [Co(BPMP)(μ-SH)(MeCN)](BF) (1a), [Co(BPMP)(SH)](BF) (1b), and [Co(PhBIMP)(μ-SH)(X)](BF) [X = DMF (2a), MeCN (2c)], while the substrates are mostly converted to the corresponding alcohols/phenols. This convenient desulfurization process has been demonstrated for 25 substrates in 6 different solvents at room temperature.

Synthesis and reactivity of a series of thiolate/thiocarboxylate bridged dicobalt(II) complexes were investigated in comparison with their carboxylate bridged analogues bearing free thiol/hydroxyl groups. Upon one-electron oxidation, complexes [Co(N-Et-HPTB)(μ-SR)](BF) (R = Ph, 1a; Et, 1b; Py, 1c) and [Co(N-Et-HPTB)(μ-SCOR)](BF) (R = Ph, 2a; Me, 2b) yielded [Co(N-Et-HPTB)(DMF)](BF) (6) (DMF = dimethylformamide) along with the corresponding disulfides (where N-Et-HPTB is the anion of N,N,N',N'-tetrakis[2-(1-ethylbenzimidazolyl)]-2-hydroxy-1,3-diaminopropane). Unlike the inertness of carboxylate bridged complexes [Co(N-Et-HPTB)(μ-OC-R-SH)](BF) (R = Ph, 3a; CHCH, 3b) and [Co(N-Et-HPTB)(μ-OCR)](BF) (R = Ph, 4a; Me, 4b; CHCHCHOH, 5) toward O, the bridging ethanethiolate in 1b was oxidized to yield a sulfinate bridged complex, [Co(N-Et-HPTB)(μ-OSEt)](BF) (10). Detailed investigation of the synthetic aspects of 1a-1c led to the discovery of a C-S bond cleavage reaction and yielded the dicobalt(II) complexes [Co(N-Et-HPTB)(SH)(HO)](BF) (8a), [Co(N-CHPy-HPTB)(SH)(HO)](BF) (8b) (where N-CHPy-HPTB is the anion of N,N,N',N'-tetrakis[2-(1-picolylbenzimidazolyl)]-2-hydroxy-1,3-diaminopropane)), and [Co(N-Et-HPTB)(μ-S)](BF) (9). Both 8a and 8b feature nonheme dinuclear Co(II) units containing a terminal hydrosulfide. The present study thus reports comparative redox reactions for a rare class of 16 dicobalt(II) complexes and introduces a selective synthetic strategy for the synthesis of unprecedented dicobalt(II) complexes featuring only one terminal hydrosulfide.

The reduction of NO to N2O by flavodiiron nitric oxide reductases (FNORs) is related to the disruption of the defense mechanism in mammals against invading pathogens. The proposed mechanism for this catalytic reaction involves both nonheme mono- and dinitrosyl diiron­(II) species as the key intermediates. Recently, we reported an initial account for NO reduction activity of an unprecedented mononitrosyl diiron­(II) complex, [Fe2(N-Et-HPTB)­(NO)­(DMF)3]­(BF4)3 (1) (N-Et-HPTB is the anion of N,N,N′,N′-tetrakis­(2-(l-ethylbenzimidazolyl))-2-hydroxy-1,3-diaminopropane; DMF = dimethylformamide) with [FeII{FeNO}7] formulation [J. Am. Chem. Soc.201713914380]. Here we report the full account for the selective synthesis, characterization, and reactivity of FNOR model complexes, which include a dinitrosyl diiron­(II) complex, [Fe2(N-Et-HPTB)­(NO)2(DMF)2]­(BF4)3 (2) with [{FeNO}7]2 formulation and a related, mixed-valent diiron­(II, III) complex, [Fe2(N-Et-HPTB)­(OH)­(DMF)3]­(BF4)3 (3). Importantly, whereas complex 2 is able to produce 89% of N2O via a semireduced mechanism (1 equiv of CoCp2 per dimer = 50% of NO reduced), complex 1, under the same conditions (0.5 equiv of CoCp2 per dimer = 50% of NO reduced), generates only ∼50% of N2O. The mononitrosyl complex therefore requires superreduction for quantitative N2O generation, which constitutes an interesting dichotomy between 1 and 2. Reaction products obtained after N2O generation by 2 using 1 and 2 equiv of reductant were characterized by molecular structure determination and electron paramagnetic resonance spectroscopy. Despite several available literature reports on N2O generation by diiron complexes, this is the first case where the end products from these reactions could be characterized unambiguously, which clarifies a number of tantalizing observations about the nature of these products in the literature.

Reduction of nitric oxide (NO) to nitrous oxide (N2O) is associated with immense biological and health implications. Flavodiiron nitric oxide reductases (FNORs) are diiron containing enzymes that catalyze the two...

Designing an efficient catalyst for a sustainable photoelectrochemical water oxidation reaction is very challenging in the context of renewable energy research. Here, we have introduced a new semiconducting porous zinc–thiolate framework via successful stitching of an “N” donor linker with a triazine-based tristhiolate secondary building unit in the overall architecture. The introduction of both linker and tristhiolate ligand synergistically modifies the architecture by making it a rigid, crystalline, three-dimensional, thermally stable, and porous framework. Our novel zinc–thiolate framework is used as an n-type semiconductor as revealed from the solid-state UV–vis DRS spectroscopic analysis, ac and dc conductivity analysis, and Mott–Schottky plot. This n-type semiconductor-based zinc–thiolate framework is utilized in the photoelectrochemical water oxidation reaction. It displayed a very high efficiency for a visible-light-driven oxygen evolution reaction (OER) in a KOH medium using standard Ag/AgCl as the reference electrode. The superiority of this material was further revealed from the low onset potential (0.822 mV vs RHE), high photocurrent density (0.204 mA cm–2), good stability, and high O2 evolution rate (77 μmol g–1 of oxygen evolution within 2 h), and a good efficiency (ABPE 0.42%, IPCE 29.6% and APCE 34.5%). Furthermore, the porosity in the overall framework seems to be a blessing to the photoelectrochemical performance due to better mass diffusion of the electrolyte. A detailed mechanism for the OER reaction was analyzed through density functional theory analysis suggesting the potential future of this Zn–thiolate framework for achieving a high efficiency in the sustainable water oxidation reaction.

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Low-dimensional materials with broken inversion symmetry and strong spin-orbit coupling can give rise to fascinating quantum phases and phase transitions. Here we report coexistence of superconductivity and ferromagnetism below 2.5 K in the quasione dimensional crystals of non-centrosymmetric (TaSe 4 ) 3 I (space group: P 42 1 c). The unique phase is a direct consequence of inversion symmetry breaking as the same material also stabilizes in a centro-symmetric structure (space group: P 4/mnc) where it behaves like a non-magnetic insulator [1][2][3][4]. The coexistence here upfront contradicts the popular belief that superconductivity and ferromagnetism are two apparently antagonistic phenomena. Notably, here, for the first time, we have clearly detected Meissner effect in the superconducting state despite the coexisting ferromagnetic order. The coexistence of superconductivity and ferromagnetism projects non-centrosymmetric (TaSe 4 ) 3 I as a host for complex ground states of quantum matter including possible unconventional superconductivity with elusive spin-triplet pairing [5][6][7][8].