Iron(II)–alkoxide and –aryloxide complexes of a tris(thioether)borate ligand: synthesis, molecular structures, and implications on the origin of instability of their iron(II)–catecholate counterpart

The phenyltris[(tert-butylthio)methyl]borate ligand, [PhTt tBu], has been studied extensively as a platform for coordination, organometallic, and bioinorganic chemistry, especially with 3d metals. While [PhTt tBu]Co(3,5-DBCatH) (3,5-DBCatH is 3,5-di-tert-butylcatecholate), a CoII–monoanionic catecholate complex, was successfully isolated to model the active site of cobalt(II)-substituted homoprotocatechuate 2,3-dioxygenase (Co-HPCD) [Wang et al. (2019). Inorg. Chim. Acta, 488, 49–55], its iron(II) counterpart, [PhTt tBu]Fe(3,5-DBCatH), was not accessible via similar synthetic routes. Switching the nucleophile from catecholate to alkoxide or aryloxide, however, led to the successful isolation of three highly air-sensitive FeII–alkoxide and –aryloxide complexes, namely, (triphenylmethoxo){tris[(tert-butylsulfanyl)methyl]phenylborato-κ3 S,S′,S′′}iron(II), [Fe(C21H38BS3)(C19H15O)], (2), (2,6-dimethylphenolato){tris[(tert-butylsulfanyl)methyl]phenylborato-κ3 S,S′,S′′}iron(II), [Fe(C21H38BS3)(C8H9O)], (3), and bis{μ-tris[(tert-butylsulfanyl)methyl]phenylborato-κ3 S,S′:S′′}bis[(phenolato-κO)iron(II)] toluene disolvate, [Fe2(C21H38BS3)2(C6H5O)2]·2C7H8, (4). In the solid state, compounds (2) and (3) are monomeric, with [PhTt tBu] acting as a tridentate ligand. In contrast, compound (4) crystallizes as a dimeric complex, wherein each [PhTt tBu] ligand binds to an iron centre with two thioethers and binds to the other iron centre with the third thioether. The molecular structures of (2)–(4) demonstrate a diversity in the binding modes of [PhTt tBu] and highlight its potential use for assembling multinuclear complexes. In addition, the successful isolation of (2)–(4), as well as the structural information of a [PhTt tBu] modification product, namely, bis{μ-tris[(tert-butylsulfanyl)methyl](2-oxidophenolato)borato-κO,O′,S,S′:O′}dicobalt(II), [Co2(C21H37BO2S3)2], (5), obtained from the reaction of [PhTt tBu]CoCl with potassium monoanionic catecholate, shed light on the origin of the instability of [PhTt tBu]Fe(3,5-DBCatH).

4′,4′′′,4′′′′′-Nitrilotris(4-methoxy-[1,1′-biphenyl]-3-carbaldehyde)

Multipodal salicylaldehydes have attracted much scientific interest as scaffolds for the construction of multinuclear complexes, as well as metal and covalent organic frameworks. Herein, we report a preparation of 4′,4′′′,4′′′′′-nitrilotris(4-methoxy-[1,1′-biphenyl]-3-carbaldehyde), a direct precursor for the tripodal salicylaldehyde with triphenylamine core. The structure of the product was confirmed by molecular spectroscopy. The reported approach may be broadened over a variety of multipodal salicylaldehydes.

Synthesis, Characterization and Antiproliferative Evaluation of Pt(II) and Pd(II) Complexes with a Thiazine-Pyridine Derivative Ligand

Chemical, pharmacological, and clinical research on anticancer coordination complexes has led to noteworthy anticancer drugs such as cisplatin, carboplatin and oxaliplatin. Although these compounds are effective chemotherapeutic agents in the treatment of different tumors, they are associated with high toxicity and numerous side effects. Several studies have shown that the range of platinum complexes with antitumor activity is not limited to structural analogs of cisplatin. Therefore, the development of convenient anticancer drugs that can be effectively used for the treatment of human tumors has become the main goal of most research groups in this field. In this sense, active platinum complexes without NH groups, transplatinum complexes, multinuclear complexes, cationic complexes, and several classes of palladium(II) complexes have emerged. Herein, the synthesis and characterization of two Pt(II) or Pd(II) complexes with PyTz (2-(2-pyridyl)iminotetrahydro-1,3-thiazine), a thiazine derivative ligand, with the formula [MCl2(PyTz)]·C2H6O (M = Pt(II) or Pd(II)) were reported. The potential anticancer ability of both complexes was evaluated in epithelial cervix carcinoma HeLa, human ovary adenocarcinoma SK-OV-3, human histiocytic lymphoma U-937, and human promyelocytic leukemia HL-60 cell lines. Interestingly, the Pt(II) complex showed great cytotoxic potential against all tumor cell lines tested, whereas the Pd(II) complex displayed slight antitumor actions.

Self-Assembled Multinuclear Complexes for Cobalt(II/III) Mediated Sensitized Solar Cells

In this work, we designed a tetranuclear self-assembled dye 4 (2Z907-Ag+-(Ru(TMAM))) exploiting a combination of the antenna effect and positively-charged groups designed to repel the oxidized form of cationic cobalt redox mediators, in order to reduce recombination and increase the efficiency of dye sensitized solar cells (DSSCs). Charge transfer and excited dynamics were probed by photoelectrochemical and photophysical measurements. The sensitized cell performance, recorded with a [Co(bpy)3]3+/2+ redox mediator and PEDOT counter electrode, showed an improvement when passing from Z907 to the multinuclear systems. The enhancement of the efficiency compared to Z907 resulted mainly from a superior steric and electrostatic shielding determined by the simultaneous presence of long alkyl chains and quaternary ammonia ion units in the architecture of 4.