Dalton Transactions

doi: 10.1039/d3dt90007jpmid: N/A

doi: 10.1039/d3dt90008hpmid: N/A

doi: 10.1039/d3dt90009fpmid: N/A

Mironov, V. S.; Bazhenova, T. A.; Manakin, Yu. V.; Yagubskii, E. B.

doi: 10.1039/d2dt02954epmid: 36537237

This article overviews the current state and prospects of the concept of advanced single-molecule magnets (SMMs) based on low-spin (S = 1/2) pentagonal-bipyramidal (PBP) 4d3 and 5d3 complexes with unquenched orbital angular momentum. This approach is based on the unique property of PBP 4d3 and 5d3 complexes to cause highly anisotropic spin coupling of perfect uniaxial symmetry, −JzSziSzj − Jxy(SxiSxj + SyiSyj), regardless of the local geometric symmetry. The M(4d/5d)–M(3d) exchange-coupled pairs in the apical positions of the PBP complexes produce Ising-type exchange interactions (|Jz| > |Jxy|), which serve as a powerful source of uniaxial magnetic anisotropy of a SMM cluster. In polynuclear heterometallic 4d/5d–3d complexes embodying PBP 4d/5d units and high-spin 3d ions, anisotropic Ising-type exchange interactions produce a double-well potential with high energy barriers Ueff, which is controlled by the anisotropic exchange parameters Jz, Jxy. Theoretical analysis shows that the barrier is proportional to the difference |Jz − Jxy| and to the number n of the apical 4d/5d–3d pairs in a SMM cluster, Ueff ∝ |Jz − Jxy|n, which provides an opportunity to scale up the barrier Ueff and blocking temperature TB up to the record values. A novel family of 4d/5d complexes with forced PBP coordination provided by structurally rigid planar pentadentate Schiff-base ligands in the equatorial plane is discussed as a better alternative to the cyanometallates. The possibility of a significant increase in the anisotropic exchange parameters Jz, Jxy in PBP complexes with monoatomic apical μ-bridging ligands is examined. The basic principles of molecular engineering the highest barrier through anisotropic exchange interactions of PBP 4d/5d complexes are formulated. The theoretical and experimental results taken together indicate that the concept of high-performance SMMs based on 4d/5d PBP complexes with unquenched orbital angular momentum is an attractive alternative to the currently dominant lanthanide-based SMM strategy.

Monika, ; Sarkar, Aniruddha; Karmodak, Naiwrit; Dhar, Basab Bijayi; Adhikari, Sanjay

doi: 10.1039/d2dt03242bpmid: 36537082

Cu(ii) complexes supported by tetradentate amido-quinoline acyclic ligands (L1 & L2) have been synthesized, characterized, and employed as catalysts for aromatic C–H hydroxylation using H2O2 as an oxidant in the absence of an external base with a high selectivity of around 90% for phenols via the non-radical pathway (TON ≥720). The KIE value, various spectroscopic studies and DFT calculation supported the involvement of Cu(ii)–OOH species.

Izarova, Natalya V.; Faassen, Fabian; Kögerler, Paul

doi: 10.1039/d2dt02922gpmid: 36537263

Solution-stable tris(hydroxymethyl)aminomethane-functionalized FeIII-containing polyoxotungstates exhibit an unusual anchoring mode of triol moieties, with one –NH2 and one –CH2OH group remaining accessible for post-functionalization or chemisorption. The redox-active title compounds have been isolated under unusually mild reaction conditions and characterized in the solid state and in aqueous solutions.

Tabernero, Vanessa; Teresa Muñoz, M.; Palenzuela, Miguel; Gomila, Rosa M.; Frontera, Antonio; Mosquera, Marta E. G.

doi: 10.1039/d2dt03581bpmid: 36594397

This communication reports the synthesis and X-ray characterization of a new mononuclear aluminium compound exhibiting an intramolecular σ-hole triel bonding interaction. It is compared with a dinuclear aluminium compound, previously reported by us, where the aluminium atoms participate in two concurrent σ-hole triel bonding interactions. To our knowledge, such behaviour has not been previously described in the literature.

Pan, Hui; Wang, Fang; She, Shixiong; Zhang, Zhengguo; Min, Shixiong

doi: 10.1039/d2dt03685apmid: 36597855

Herein, we report an effective strategy for improving the electrocatalytic CO2 reduction reaction (CO2RR) performance of a Zn foil electrode via concurrent surface reconstruction and interfacial surfactant modification. The oxide-derived and CTAB-modified Zn electrode (OD-Zn-CTAB) prepared by electrochemically reducing the air-annealed Zn foil electrode in the presence of CTAB exhibits high electrocatalytic activity and selectivity for CO production with a CO partial current density (jCO) of 8.2 mA cm−2 and a CO faradaic efficiency (FECO) of 90% at −1.0 V vs. the reversible hydrogen electrode (RHE), greatly outperforming the pristine Zn foil (FECO = 32.0%; jCO = 0.5 mA cm−2) and OD-Zn (FECO = 77.6%; jCO = 5.0 mA cm−2) obtained by electroreduction of annealed Zn. The greatly enhanced CO2RR performance of OD-Zn-CTAB can be attributed to the increased number of active sites originating from the surface reconstruction and the formation of a favorable CTAB-modified electrode/electrolyte (E/E) interface that can efficiently adsorb and activate CO2 while inhibiting the competitive H2 evolution reaction.

Lin, Rong-Yan; Deng, Lan; An, Dong-Li; Zhou, Zhao-Hui

doi: 10.1039/d2dt03324kpmid: 36416137

By adjusting the pH values of the solutions, binuclear, tetranuclear and hexadecanuclear glycolato thio- and oxomolybdenum(v/iv) complexes [MoV2O2(μ2-O)(μ2-S)(Hglyc)2(Hpz)2]·H2O (1, H2glyc = glycolic acid, Hpz = pyrazole), (Hdpa)[MoV2O2(μ2-S)2(Hglyc)(glyc)(H2O)] (2, dpa = 2,2′-dipyridylamine), (Hdpa)4[MoV4O4(μ3-O)2(μ2-S)2(glyc)2(S2O3)2] (3) and Na2[MoIV4MoV12O12(μ2-O)6(μ2-OH)2(μ3-O)12(glyc)4(Hpz)4(pz)8]·28H2O (4) have been obtained successfully. Here the glycolates existed in varying aggregates with different degrees of protonation and deprotonation in 1–4. The stable formations of 1 and 2 are attributed to strong hydrogen bonds formed between the molecules. In particular, the asymmetric unit in 2 is a tetramer linked by hydrogen bonding [2.574(9) Å] between α-hydroxy and α-alkoxy groups for further construction of unsaturated penta-coordination environments. Moreover, deprotonated glycolates act as bridging ligands to form tetra- and hexadecanuclear compounds 3 and 4, respectively. The smallest unit in 4 exhibits mixed valences of 4+ and 5+ simultaneously, where its gas adsorption experiments manifest that 4 is obviously beneficial for O2 and CO2 compared with no adsorption of N2, CH4 and H2 at different pressures.

Matsubara, Kouki; Yamada, Yuji; Iwasaki, Haruka; Ikeda, Hayao; Kanetsugu, Yuki; Kawata, Satoshi; Koga, Yuji

doi: 10.1039/d2dt03617gpmid: 36537300

Iron complexes bearing 1,2,3-triazol-5-ylidene were synthesized and applied to the reaction with hydrosilane and homogeneous catalytic hydrosilylation of aromatic ketones and aldehydes. Addition of a free carbene to a solution of Fe(CO)4Br2 yielded an octahedral, diamagnetic and cationic iron(ii) complex [Fe(1,2,3-triazolylidene)(CO)2Br]+. Pyrolysis of the dicarbonyl complex eliminated the two CO ligands to form a paramagnetic four-coordinate complex. A theoretical study using DFT calculations indicated that the spin state changed from singlet to quintet during ligand elimination. Investigations of the successful hydrosilylation of acetophenone and benzaldehyde derivatives using MIC–iron(ii) bromide suggested the importance of the base for efficient conversion in the catalytic process. The bromide-to-hydride exchange reaction, transmetallation, of MIC–iron(ii) bromide in the presence of KOtBu and HSi(OEt)3 which could occur in the initial process of hydrosilylation was proposed, and supported by a theoretical study.