Trimetallic Complexes Research Articles

Reactivity of [(Cp*CoPh)(Cp*Co)(μ-TePh)(μ-k2-Te,H-TeBH3)] Toward [M(CO)5·THF] (M = Mo and W), CS2, and [Fe2(CO)9

Syntheses and structural elucidation of homo- and heterochalcogen-bridged complexes of cobalt are described. The photolytic reaction of bimetallic hydridoborate species [(Cp*CoPh)(Cp*Co)(μ-TePh)(μ-k2-Te,H-TeBH3)] (1) in the presence of [M(CO)5·THF] (M = Mo and W) afforded unprecedented tellurolate-bridged [(Cp*Co)2(μ-TePh)3]+[TePh{M(CO)5}2]- (M = Mo (2), W (3)) as ionic complexes with the release of BH3. Complex 2 has three bridged-TePh moieties between two Cp*Co fragments in the cation part, whereas the anionic part, [TePh{M(CO)5}2]-, shows a distorted trigonal pyramidal core. In order to synthesize mixed chalcogenate-bridged complexes having both S and Te, we carried out the photolytic reaction of 1 with CS2. Although the objective of generating mixed chalcogen-bridged complex [(Cp*Co)2(μ-TePh)2(μ-S)] was not achieved, the reaction yielded an unusual bimetallic thiotellurite complex [(Cp*Co)2(μ-S3TeS3-κ2S:κ2Te:κ2S')] (4). Complex 4 has two wings, each consisting of three sulfur atoms, that are connected to two Co-atoms and one Te-atom. Further, to synthesize the Fe analogue of 2 and 3, a similar reaction was carried out with [Fe2(CO)9]. However, the reaction led to the formation of the trimetallic complex [Cp*Co(CO)(μ3-Te)2{Fe2(CO)6}] (5). These complexes were characterized by employing different multinuclear NMR, IR spectroscopies, single-crystal X-ray diffraction analyses, and mass spectrometry. Additionally, computational analyses of these chalcogen-bridged neutral and ionic complexes were conducted to offer insight into their bonding.

Selective B(3)-H Activation Affording Multinuclear Ir(III) Complexes with (o-Carboranyl)dithioester Ligands.

A method was developed to link two or three o-carborane moieties to form a series of carboranyl dithioester bridging ligands via in situ substitution of haloalkanes by tetraphenylphosphonium carboranyldithiocarboxylates. Based on these ligands, direct B-H activation without the assistance of Ag(I) and alkali was successfully achieved with half-sandwich Ir(III) substrate [Cp*IrCl2]2 to yield corresponding bimetallic or trimetallic complexes. Single crystal structure analyses of the B-H activated complexes and corresponding SnCl2-inserted derivatives confirm the selective B(3)-H activation in these complexes.

Development of (NO)Fe(N2S2) as a Metallodithiolate Spin Probe Ligand: A Case Study Approach.

ConspectusThe ubiquity of sulfur-metal connections in nature inspires the design of bi- and multimetallic systems in synthetic inorganic chemistry. Common motifs for biocatalysts developed in evolutionary biology include the placement of metals in close proximity with flexible sulfur bridges as well as the presence of π-acidic/delocalizing ligands. This Account will delve into the development of a (NO)Fe(N2S2) metallodithiolate ligand that harnesses these principles. The Fe(NO) unit is the centroid of a N2S2 donor field, which as a whole is capable of serving as a redox-active, bidentate S-donor ligand. Its paramagnetism as well as the ν(NO) vibrational monitor can be exploited in the development of new classes of heterobimetallic complexes. We offer four examples in which the unpaired electron on the {Fe(NO)}7 unit is spin-paired with adjacent paramagnets in proximal and distal positions.First, the exceptional stability of the (NO)Fe(N2S2)-Fe(NO)2 platform, which permits its isolation and structural characterization at three distinct redox levels, is linked to the charge delocalization occurring on both the Fe(NO) and the Fe(NO)2 supports. This accommodates the formation of a rare nonheme {Fe(NO)}8 triplet state, with a linear configuration. A subsequent FeNi complex, featuring redox-active ligands on both metals (NO on iron and dithiolene on nickel), displayed unexpected physical properties. Our research showed good reversibility in two redox processes, allowing isolation in reduced and oxidized forms. Various spectroscopic and crystallographic analyses confirmed these states, and Mössbauer data supported the redox change at the iron site upon reduction. Oxidation of the complex produced a dimeric dication, revealing an intriguing magnetic behavior. The monomer appears as a spin-coupled diradical between {Fe(NO)}7 and the nickel dithiolene monoradical, while dimerization couples the latter radical units via a Ni2S2 rhomb. Magnetic data (SQUID) on the dimer dication found a singlet ground state with a thermally accessible triplet state that is responsible for magnetism. A theoretical model built on an H4 chain explains this unexpected ferromagnetic low-energy triplet state arising from the antiferromagnetic coupling of a four-radical molecular conglomerate. For comparison, two (NO)Fe(N2S2) were connected through diamagnetic group 10 cations producing diradical trimetallic complexes. Antiferromagnetic coupling is observed between {Fe(NO)}7 units, with exchange coupling constants (J) of -3, -23, and -124 cm-1 for NiII, PdII, and PtII, respectively. This trend is explained by the enhanced covalency and polarizability of sulfur-dense metallodithiolate ligands. A central paramagnetic trans-Cr(NO)(MeCN) receiver unit core results in a cissoid structural topology, influenced by the stereoactivity of the lone pair(s) on the sulfur donors. This {Cr(NO)}5 radical bridge, unlike all previous cases, finds the coupling between the distal Fe(NO) radicals to be ferromagnetic (J = 24 cm-1).The stability and predictability of this S = 1/2 moiety and the steric/electronic properties of the bridging thiolate sulfurs suggest it to be a likely candidate for the development of novel molecular (magnetic) compounds and possibly materials. The role of synthetic inorganic chemistry in designing synthons that permit connections of the (NO)Fe(N2S2) metalloligand is highlighted as well as the properties of the heterobi- and polymetallic complexes derived therefrom.

Coupling between two Ru(bda) catalysts bridged by a trans-dicyano complex.

We have prepared two trimetallic complexes [{Ru(bda)(DMSO)(μ-CN)}2Ru(L)4] (with bda = 2,2'-bipyridine-6,6'-dicarboxylate) where two {Ru(bda)} centers are bridged by a cyanide complex of the trans-Ru(L)4CN2 family (with L = pyridine and 4-tert-butylpyridine). The complex [{Ru(bda)(DMSO)(μ-CN)}2Ru(py)4] is fully soluble in aqueous solution and is a catalyst for the oxidation of water both chemically, using Ce(IV) at pH = 1 as the terminal oxidant, and electrochemically. Both reactions are first order in the complex and the resting state of the catalyst is the [RuVRuIII(py)4RuIV]2+ redox state. Electrochemical and spectroelectrochemical studies together with (TD)DFT calculations show that the coupling between the Ru(bda) fragments for the [RuIIIRuII(py)4RuIII]2+ and [RuIVRuII(py)4RuIV]2+ redox states is very weak, but significant for the [RuVRuII(py)4RuIV]2+ ion due to the orientation of the orbitals involved. This coupling affects the reactivity of the [RuVRuII(py)4RuIV]2+ redox state, making it a much slower catalyst towards the water oxidation reaction than [RuVRuIII(py)4RuIV]2+.

Synthesis and luminescent properties of hetero-bimetallic and hetero-trimetallic Ru(II)/Au(I) or Ir(III)/Au(I) complexes.

A series of Ru(II) and Ir(III) based photoluminescent complexes were synthesised that incorporate an ancillary 2,2'-bipyridine ligand adorned with either one or two pendant N-methyl imidazolium groups. These complexes have been fully characterised by an array of spectroscopic and analytical techniques. One Ir(III) example was unequivocally structurally characterised in the solid state using single crystal X-ray diffraction confirming the proposed formulation and coordination sphere. These complexes were then transformed into their heterometallic, Au(I)-containing, analogues in two steps to yield either bi- or trimetallic complexes that integrate {Au(PPh3)}+ units. X-ray diffraction was used to corroborate the solid state structure of the hetero bimetallic complex, based upon a Ru(II)-Au(I) species. The heterometallic complexes all displayed red photoluminescent features (λem = 616-629 nm) that were consistent with the parent Ru(II) or Ir(III) lumophores in each case. The modulation of the emission from the Ru(II)-Au(I) complexes was much more strongly evident than for the Ir(III)-Au(I) analogues, which is ascribed to the inherent differences in the specific triplet excited state character of the emitting states within each heterometallic species.

Dinitrogen reduction chemistry with scandium provides a complex with two side-on (N[double bond, length as m-dash]N)2- ligands bound to one metal: (C5Me5)Sc[(µ-η2:η2-N2)Sc(C5Me5)2]2.

Although there are few reduced dinitrogen complexes of scandium, this metal has revealed a new structural type in reductive dinitrogen chemistry by reduction of bis(pentamethylcyclopentadienyl) scandium halides under N2. Reduction of (Cp* = C5Me5) with potassium graphite (KC8) under dinitrogen generates the dark blue paramagnetic complex , 1. This end-on bridging (N[double bond, length as m-dash]N)2- complex is a diradical with a magnetic moment of 2.8µ B. Upon further reduction of 1 with KC8, the orange diamagnetic trimetallic complex , 2, is obtained. This complex has an unprecedented structure in which two side-on bridging (N[double bond, length as m-dash]N)2- ligands are bound to the central (Cp*Sc)2+ moiety. Complex 2 can also be obtained directly from reduction of or a mixture of and with KC8. The reaction of with KC8 in the presence of 18-crown-6 or 2.2.2-cryptand affords 2 along with small amounts of , 3, which is green at room temperature and purple at low temperature and displays a mixture of side-on and end-on bridging isomers in the crystal structure collected at -180 °C. Density functional theory (DFT) calculations are consistent with a triplet ground state for the end-on complex 1 and singlet ground states for the side-on complexes 2 and 3.

Electronic Transition and Magnetic Coupling Regulation in Trimetallic Complexes Featuring a New Bridging Ligand Obtained by Oxidative Addition.

A series of trimetallic complexes [FeIII(μ-L)(py)]2MII(py)n (n = 2, MII = MnII, 1; FeII, 2; CoII, 3; ZnII, 4; n = 3, MII = CdII, 5) with a new bridging ligand L4- (deprotonated 1,2-N1,N2-bis(2-mercaptoanil) oxalimidic acid) were synthesized and fully characterized by elemental analysis, single-crystal X-ray crystallography, IR, and Mössbauer spectra. Interestingly, the bridging ligand was obtained by oxidative addition of the (gma•)3- ligand from the mononuclear precursor Fe(gma)py (gma = glyoxal-bis(2-mercaptoanil)). In the obtained complexes, the bridging ligand L4- coordinates to the terminal FeIII ions (intermediate-spin with SFe = 3/2) by the N, S atoms, and coordinate to the central metal MII ion by the four O atoms. The resonance structure of the bridging ligand can be described as the two 4π-electron delocalized systems connected by one single-bond (C1-C2), which is different from the electronic structure of the precursor Fe(gma)py. Remarkably, the magnetic coupling interaction can be regulated through the central metal. The ferromagnetic coupling constant J gradually decreases as MII changes from FeII to CoII and MnII, while the paramagnetic behaviors are presented when MII = ZnII and CdII, confirmed by the magnetic susceptibility measurements and further supported by using the PHI program. Furthermore, the bridging ligand to the terminal FeIII charge transfer (LMCT) transitions emerged in all complexes but the central FeII to terminal FeIII charge transfer (MMCT) only presented in complex 2, strongly supported by the UV/vis-NIR electronic spectra and TDDFT calculations.

Magnetic Anisotropy Transfer from Mono‐ to Polymetallic Complexes

AbstractThe reaction of multi‐bidentate oxamate‐based copper(II) complexes with the [Ni(iPrtacn)Cl2] complex (iPrtacn:1,4,7‐triisopropyl‐1,4,7‐triazacyclononane) has been investigated. X‐ray diffraction studies reveal that for all compounds the oxamato κO,κΟ’ bidentate coordination site replaces the two chloride ions in [Ni(iPrtacn)Cl2] to form trimetallic {CuNi2} (1–3), hexametallic {Cu2Ni4} (4) and enneametallic {Cu3Ni6} (5) complexes. The investigation of the magnetic properties shows that Cu−Ni interactions through the oxamato bridge are in the expected range (−111 cm−1, −68 cm−1). For 1–3, both the sign and strength of the magnetic couplings are computed independently from DFT calculations, and these estimates broadly agree with the experiments. The magnetization measurements and EPR studies reveal that 1–3 are anisotropic: a significant portion of the large anisotropy of the [Ni(iPrtacn)Cl2] complex is retained, resulting in a D value for the S=3/2 ground state of 5 cm−1 on average. This is no longer the case for 4 and 5 where the anisotropy of the Ni(II) complexes is diluted due to the high nuclearity of the final edifices. These results show that it is possible to obtain trimetallic complexes with a high anisotropy and a high spin value for the ground state by a judicious choice of the interacting metal ions.

Controlled Supramolecular Self-Assembly of Uniform Nanostructures from Trimetallic Complexes

The self-assembly of a tris-salphen complex afforded supramolecular nanofibers with a narrow length distribution. Nanofiber lengths could be easily tuned with the self-assembly conditions while maintaining low dispersity. The crystal structure of the complex and density functional theory (DFT) calculations suggested the presence of a metastable aggregate which reorients on heating to afford longer supramolecular nanofibers. The surprising, controlled molecular assembly of these complexes may pave the way to well-defined nanostructures for catalysis, electronics, and optical applications.

Metal‐Mediated Oligomerization Reactions of the Cyaphide Anion

AbstractThe cyaphide anion, CP−, is shown to undergo three distinct oligomerization reactions in the coordination sphere of metals. Reductive coupling of Au(IDipp)(CP) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) by Sm(Cp*)2(OEt2) (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl), was found to afford a tetra‐metallic complex containing a 2,3‐diphosphabutadiene‐1,1,4,4‐tetraide fragment. By contrast, non‐reductive dimerization of Ni(SIDipp)(Cp)(CP) (SIDipp=1,3‐bis(2,6‐diisopropylphenyl)‐imidazolidin‐2‐ylidene; Cp=cyclopentadienyl), gives rise to an asymmetric bimetallic complex containing a 1,3‐diphosphacyclobutadiene‐2,4‐diide moiety. Spontaneous trimerization of Sc(Cp*)2(CP) results in the formation of a trimetallic complex containing a 1,3,5‐triphosphabenzene‐2,4,6‐triide fragment. These transformations show that while cyaphido transition metal complexes can be readily accessed using metathesis reactions, many such species are unstable to further oligomerization processes.

Metal-Mediated Oligomerization Reactions of the Cyaphide Anion.

The cyaphide anion, CP- , is shown to undergo three distinct oligomerization reactions in the coordination sphere of metals. Reductive coupling of Au(IDipp)(CP) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) by Sm(Cp*)2 (OEt2 ) (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl), was found to afford a tetra-metallic complex containing a 2,3-diphosphabutadiene-1,1,4,4-tetraide fragment. By contrast, non-reductive dimerization of Ni(SIDipp)(Cp)(CP) (SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolidin-2-ylidene; Cp=cyclopentadienyl), gives rise to an asymmetric bimetallic complex containing a 1,3-diphosphacyclobutadiene-2,4-diide moiety. Spontaneous trimerization of Sc(Cp*)2 (CP) results in the formation of a trimetallic complex containing a 1,3,5-triphosphabenzene-2,4,6-triide fragment. These transformations show that while cyaphido transition metal complexes can be readily accessed using metathesis reactions, many such species are unstable to further oligomerization processes.

Magnetic coupling between Fe(NO) spin probe ligands through diamagnetic NiII, PdII and PtII tetrathiolate bridges.

Reaction of the nitrosylated-iron metallodithiolate ligand, paramagnetic (NO)Fe(N2S2), with [M(CH3CN)n][BF4]2 salts (M = NiII, PdII, and PtII; n = 4 or 6) affords di-radical tri-metallic complexes in a stairstep type arrangement ([FeMFe]2+, M = Ni, Pd, and Pt), with the central group 10 metal held in a MS4 square plane. These isostructural compounds have nearly identical ν(NO) stretching values, isomer shifts, and electrochemical properties, but vary in their magnetic properties. Despite the intramolecular Fe⋯Fe distances of ca. 6 Å, antiferromagnetic coupling is observed between {Fe(NO)}7 units as established by magnetic susceptibility, EPR, and DFT studies. The superexchange interaction through the thiolate sulfur and central metal atoms is on the order of NiII < PdII ≪ PtII with exchange coupling constants (J) of -3, -23, and -124 cm-1, consistent with increased covalency of the M-S bonds (3d < 4d < 5d). This trend is reproduced by DFT calculations with molecular orbital analysis providing insight into the origin of the enhancement in the exchange interaction. Specifically, the magnitude of the exchange interaction correlates surprisingly well with the energy difference between the HOMO and HOMO-1 orbitals of the triplet states, which is reflected in the central metal's contribution to these orbitals. These results demonstrate the ability of sulfur-dense metallodithiolate ligands to engender strong magnetic communication by virtue of their enhanced covalency and polarizability.

Active bimetallic Fe–O–Co sites built on 2D trimetallic complex spinel oxides for industrially oxygen evolution electrocatalyst

Fabrication of active and durable non-noble metal heterogeneous electrocatalysts to settle the relatively slow kinetic process and poor stability during the oxygen evolution reaction (OER) process is of great significance. Herein, we fabricate in-situ 2D Fe-based trimetallic complex spinel oxide nanosheets (FeCoNi)O4 via a polyethylene glycol-barbituric acid deep eutectic solvent-assisted route. Multiple analytical characterizations illustrate a deep understanding of the structure and composition of (FeCoNi)O4, disclosing Fe, Co, and Ni ions occupy both tetrahedrally and octahedrally coordinated positions. Meanwhile, the synergistic actions of preparing multiple-cations substitution and constructing oxygen vacancy activate covalent Fe–O–Co bonds in (FeCoNi)O4. Due to the active bimetallic Fe–O–Co sites, enhanced electronic conductivity and unique structure stability, the synthesized 2D (FeCoNi)O4 nanosheets exhibit excellent OER performance with relatively low overpotential (421 mV for 1000 mA/cm2) and long-term stability (720 mA/cm2 for 6 h) in alkaline media, which is much better than that of Fe-based bi/monometallic spinel oxides. In-situ Raman spectra and quasi-in-situ X-ray photoelectron spectroscopy results depict that O-bridged Fe–O–Co bimetallic sites promote the formation of μ(O–O) intermediates and undergo the direct O2 evolution route, thus accelerating OER.

Synthesis and anticancer evaluation of trinuclear N^N quinolyl-benzimidazole-based PGM complexes

• Trinuclear N^N quinolyl-benzimidazole-based PGM complexes were prepared. • Comprehensively characterised using various spectroscopic and analytical techniques. • Antiproliferative properties against two human breast cancer cell lines, MCF-7 and MDA-MB-32, were evaluated. • A ruthenium(II) p -cymene complex was found to be the most active complex. The synthesis, characterization and cytotoxicity of a novel tris-benzimidazole-quinoline hybrid ligand and its corresponding cationic trimetallic complexes are described. The synthesis of the ligand was achieved via an acid-catalyzed cyclization-condensation reaction of a tris-benzenediamine precursor with 2-quinolinecarboxaldehyde. The complexation reactions of the bidentate tris-ligand with the appropriate precursor dimers [Ru(η 6 -p-Pr i C 6 H 4 Me)Cl 2 ] 2 , [IrCp*( μ -Cl)Cl] 2 , [RuCl 2 (η 6 -C 6 H 5 OCH 2 CH 2 OH)] 2 and [Os(η 6 -p-Pr i C 6 H 4 Me)Cl 2 ] 2 afforded four new cationic trimetallic complexes. The complexes are moisture and air-stable and were characterized using various spectroscopic techniques ( 1 H, 13 C NMR spectroscopy and FT-IR spectroscopy). UV/Visible spectroscopic studies of the trinuclear metal complexes showed that the complexes are stable in DMSO for 48 h at room temperature and physiological temperature, and are thus compatible for in vitro experiments. The synthesized ligand and complexes were examined for antiproliferative properties against two human breast cancer cell lines: MCF-7 and MDA-MB-231. Preliminary evaluations of the test compounds were conducted at a single dose concentration of the test compounds. The osmium(II) and ruthenium(II) p -cymene complexes showed the greatest anticancer activity of all the synthesized compounds and were selected for multidose screening. The ruthenium(II) p -cymene complex was found to be the most active complex, with IC 50 values of 25.23 μ M and 32.68 μ M in the MCF-7 and MDA-MB-231 cell lines, respectively.

Isolation and Reactivity of Tetrylene-Tetrylone-Iron Complexes Supported by Bis(N-Heterocyclic Imine) Ligands.

The germanium iron carbonyl complex 3 was prepared by the reaction of dimeric chloro(imino)germylene [IPrNGeCl]2 (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-iminato) with one equivalent of Collman's reagent (Na2 Fe(CO)4 ) at room temperature. Similarly, the reaction of chloro(imino)stannylene [IPrNSnCl]2 with Na2 Fe(CO)4 (1 equiv) resulted in the Fe(CO)4 -bridged bis(stannylene) complex 4. We observed reversible formation of bis(tetrylene) and tetrylene-tetrylone character in complexes 3 vs. 5 and 4 vs. 6, which was supported by DFT calculations. Moreover, the Li/Sn/Fe trimetallic complex 12 has been isolated from the reaction of [IPrNSnCl]2 with cyclopentadienyl iron dicarbonyl anion. The computational analysis further rationalizes the reduction pathway from these chlorotetrylenes to the corresponding complexes.

Isolation and Reactivity of Tetrylene‐Tetrylone‐Iron Complexes Supported by Bis(N‐Heterocyclic Imine) Ligands

The germanium iron carbonyl complex 3 was prepared by the reaction of dimeric chloro(imino)germylene [IPrNGeCl]2 (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-iminato) with one equivalent of Collman's reagent (Na2Fe(CO)4) at room temperature. Similarly, the reaction of chloro(imino)stannylene [IPrNSnCl]2 with Na2Fe(CO)4 (1 equiv) resulted in the Fe(CO)4-bridged bis(stannylene) complex 4. We observed reversible formation of bis(tetrylene) and tetrylene-tetrylone character in complexes 3 vs. 5 and 4 vs. 6, which was supported by DFT calculations. Moreover, the Li/Sn/Fe trimetallic complex 12 has been isolated from the reaction of [IPrNSnCl]2 with cyclopentadienyl iron dicarbonyl anion. The computational analysis further rationalizes the reduction pathway from these chlorotetrylenes to the corresponding complexes.

Trimetallic Iridium-Nickel-Iridium Bis(formazanate) Assemblies.

Formazans have attracted a lot of attention in coordination chemistry since the early 1940s because of their unique properties engendered by the nitrogen-rich conjugated backbone. Although many studies have been done using formazanates to chelate transition metals, research using formazanates as building blocks for polynuclear compounds and supramolecular chemistry remains rare. In this paper, we describe a synthetic strategy that uses a pyridyl-substituted bis(formazanato)nickel complex as a metalloligand to further assemble with two [Ir(C^N)2]+ centers (C^N is the cyclometalating ligand). The trimetallic complexes represent a new binding mode for flexidentate pyridyl-substituted formazanates and a new structural class of polynuclear formazanate complexes. This work expands the chemistry of polynuclear formazanate complexes, for the first time pairing 3d and 5d metals in the same assembly. The redox chemistry of these trimetallic complexes, evaluated via cyclic voltammetry, is described. The compounds described in this work are luminescent, and studies of bis-cyclometalated iridium model complexes lacking the formazanate bridge confirm that the phosphorescence arises from the iridium center.

Nano-Sized Antioxidative Trimetallic Complex Based on Maillard Reaction Improves the Mineral Nutrients of Apple (Malus domestica Borkh.).

The metallic complex is widely used in agricultural applications. Due to the oxidation of the metal and environmental unfriendliness of ligand, maintaining an efficient mineral supply for plants without causing environmental damage is difficult. Herein, an antioxidative trimetallic complex with high stability was synthesized by interacting Ca2+, Fe2+, and Zn2+ with the biocompatible ligands from the Maillard reaction. The composite structure elucidation was carried out by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR). Thermal stability was measured by thermogravimetric (TG). Antioxidative activities were evaluated by ferric reducing antioxidant power and radical scavenging activity assays. The three metals were successfully fabricated on the Maillard reaction products (MRPs) with contents of Ca (9.01%), Fe (8.25%), and Zn (9.67%). Microscopy images revealed that the three metals were uniformly distributed on the MRPs with partial aggregation of <30 nm. FTIR and XPS results revealed that the metals were interacted with MRPs by metal–O and metal–N bonds. TG and antioxidative activity assays showed that the trimetallic complex meets the requirements of thermodynamics and oxidation resistance of horticultural applications. Additionally, the results of the exogenous spraying experiment showed that the trimetallic complex significantly increased the mineral contents of the “Fuji” apple. By treatment with the complex, the concentrations of Ca, Fe, and Zn were increased by 85.4, 532.5, and 931.1% in the leaf; 16.0, 225.2, and 468.6% in the peel; and 117.6, 217.9, and 19.5% in the flesh, respectively. The MRP-based complexes offered a higher growth rate of the mineral content in apples than ones based on sugars or amino acids. The results of the spraying experiment carried out in 2 years show that the method has high reproducibility. This study thus promotes the development of green metallic complexes and expands the scope of agrochemical strategy.

Anion and Temperature Responsive Molecular Switches Based on Trimetallic Complexes of Ru(II) and Os(II) That Demonstrate Advanced Boolean and Fuzzy Logic Functions.

Anion- and temperature-induced alteration of the photoredox behaviors of our recently reported trimetallic complexes was carried out to fabricate potential molecular switches. The triads [(phen)2Ru(d-HIm-t)M(t-HIm-d)Ru(phen)2]6+ (phen = 1,10-phenanthroline, d-HIm-t = heterotopic bipyridine-terpyridne type bridging ligand, and M = RuII and OsII) possess two acidic imidazole NH protons that upon interaction with anions give rise to considerable changes in their photophysical and electrochemical behaviors. Red-shifts of the absorption and emission maximum and a decrease in the M3+/M2+ potential occur when the triads are treated with basic anions. In fact, the triads can function as triple-channel sensors for F-, AcO-, CN-, OH-, and H2PO4- in acetonitrile and as selective probes for CN- and SCN- in water. The equilibrium constants for the receptor-anion interaction are on the order of 106 M-1, while the limit of detection was on the order of 10-9 M. Temperature plays a key role in the luminescence properties of the triads by adjusting the energy barrier between the emitting triplet metal-to-ligand charge transfer and non-emitting triplet metal-centered levels. A decrease in temperature leads to increases in the emission intensity and lifetime of the triads displaying the "on state", whereas an increase in temperature leads to a decrease in their emission characteristics and thus indicates the "off state" and that the process is fully reversible. In essence, the triads could function as potential switches on the basis of the reversible change in their spectral and redox behaviors under the influence of anion, acid, and temperature. The most important outcome of this study is mimicking several advanced Boolean and fuzzy logic functions by utilizing the spectral response of the triads upon the action of said external stimuli.

Carbonylative Polymerization of Epoxides Mediated by Tri-metallic Complexes: A Dual Catalysis Strategy for Synthesis of Biodegradable Polyhydroxyalkanoates.

Polyhydroxyalkanoates (PHAs) are a unique class of commercially manufactured biodegradable polyesters with properties suitable for partially substituting petroleum-based plastics. However, high costs and low volumes of production have restricted their application as commodity materials. In this study, tri-metallic complexes were developed for carbonylative polymerization via a dual catalysis strategy, and 17 products of novel PHAs with up to 38.2 kg mol-1 Mn values were discovered. The polymerization proceeds in a sequential fashion, which entails the carbonylative ring expansion of epoxide to β-lactone and its subsequent ring-opening polymerization that occurs selectively at the O-alkyl bond via carboxylate species. The wide availability and structural diversity of epoxide monomers provide PHAs with various structures, excellent functionalities, and tunable properties. This study represents a rare example of the preparation of PHAs using epoxides and carbon monoxide as raw materials.