Nitrogen Ligands Research Articles

Characterization of a Proposed Terminal Iron(III) Nitride Intermediate of Nitrogen Fixation Stabilized by a Trisphosphine‐Borane Ligand

AbstractTerminal iron nitrides (Fe≡N) have been proposed as intermediates of Fe‐mediated nitrogen fixation, and well‐defined synthetic iron nitrides have been characterized in high oxidation states, including FeIV, FeV, and FeVI. This study reports the generation and low temperature characterization of a terminally bound iron(III) nitride, P3BFe(N) (P3B=tris(o‐diisopropylphosphinophenyl)borane), which is a proposed intermediate of iron‐mediated nitrogen fixation by the P3BFe‐catalyst system. CW‐ and pulse EPR spectroscopy (HYSCORE and ENDOR), supported by DFT calculations, help to define a 2A ground state electronic structure of this C3‐symmetric nitride species, placing the unpaired spin in a sigma orbital along the B−Fe−N vector; this electronic structure is distinct for an iron nitride. The unusual d5‐configuration is stabilized by significant delocalization (≈50 %) of the unpaired electron onto the axial boron and nitrogen ligands, with a majority of the spin residing on boron.

Characterization of a Proposed Terminal Iron(III) Nitride Intermediate of Nitrogen Fixation Stabilized by a Trisphosphine-Borane Ligand.

Terminal iron nitrides (Fe≡N) have been proposed as intermediates of Fe-mediated nitrogen fixation, and well-defined synthetic iron nitrides have been characterized in high oxidation states, including FeIV , FeV , and FeVI . This study reports the generation and low temperature characterization of a terminally bound iron(III) nitride, P3 B Fe(N) (P3 B =tris(o-diisopropylphosphinophenyl)borane), which is a proposed intermediate of iron-mediated nitrogen fixation by the P3 B Fe-catalyst system. CW- and pulse EPR spectroscopy (HYSCORE and ENDOR), supported by DFT calculations, help to define a 2 A ground state electronic structure of this C3 -symmetric nitride species, placing the unpaired spin in a sigma orbital along the B-Fe-N vector; this electronic structure is distinct for an iron nitride. The unusual d5 -configuration is stabilized by significant delocalization (≈50 %) of the unpaired electron onto the axial boron and nitrogen ligands, with a majority of the spin residing on boron.

A New Complex Design of Fe (II) Isoleucine Dithiocarbamate as a Novel Anticancer and Antivirus against SARSCOV-2 (COVID-19).

This study was carried out to synthesize a new complex of Fe(II) with isoleucine dithiocarbamate ligand and to determine its potential as an anticancer and antiviral agent for SARSCOV-2. The synthesized complexes were then characterized by UV-vis and FT-IR spectroscopy and their melting points. The value of the conductivity of the complex compound is also determined. Anti-cancer activity was tested in vitro and molecular docking. Its potential as an antiviral against SARSCOV-2 was also carried out by molecular docking. Pharmacokinetics/ADMET properties were also carried out on the complex. Spectral results showed the successful synthesis of Fe(II) isoleucine dithiocarbamate complex. The complex produced UV-vis spectra at 268 and 575 nm, and the IR data at 399-599 cm-1 showed the coordination between the Fe(II) atoms with sulphur, nitrogen and oxygen of the isoleucine dithiocarbamate ligand. Fe(II) isoleucine dithiocarbamate had a cytotoxicity effect on the MCF-7 cell line (IC50 =613 µg/mL). The complex significantly caused morphological changes in the breast cancer cell line, finally leading to cell apoptosis. Cytotoxic test of Fe(II) isoleucine dithiocarbamate showed moderate anticancer activity on MCF-7 cancer cells and showed antiviral activity against SARSCOV-2 by interfering with spike glycoprotein -ACE2 receptors, and inhibiting major proteases and 3Clpro.

Copper (II) complexes with N, S donor pyrazole-based ligands as anticancer agents.

A group of bidentate nitrogen and sulfur donor pyrazole derivative ligands abbreviated as Na[RNCS(Pz)], Na[RNCS(PzMe2)], Na[RNCS(PzMe3)], Na[RNCS(PzPhMe)], Na[RNCS(PzPh2)], where (R = Et, Ph), and their Cu (II) complexes were synthesized and characterized by spectroscopic and physicochemical methods. The crystal structure of [Cu(PhNCSPzMe3)2] was determined by X-ray crystallography analysis and the results described a distorted square planar coordination geometry for this complex. Also, the cyclic voltammetry investigations indicated that the synthesized copper complex is an electrochemically active species. Moreover, the cytotoxic activity of all of the twenty synthesized compounds was evaluated using MTT assay against the MCF-7 (human breast carcinoma) cell lines, in vitro. Cu (II) complexes indicate significant cytotoxicity against the MCF-7 cell lines as compared with the free ligands. The docking studies showed that the copper complexes have better interactions with EGFR and CDK2 proteins, compared to the free ligands, and most of the studied compounds have a higher value of binding energy relative to the studied controls. The results of QSAR analysis suggest that dipole moment is in direct correlation with the obtained IC50 values, and it strongly impact the anticancer effects generated by the compounds. Our findings suggest that the developed copper complexes can be good candidates for further evaluations as chemotherapeutic agents in the treatment of cancer.

Synthesis, Structure and Thermal Properties of Volatile Indium and Gallium Triazenides**

AbstractIndium and gallium nitride are important semi‐conductor materials with desirable properties for high‐frequency and power electronics. We have previously demonstrated high‐quality ALD grown InN and GaN using the hexacoordinated 1,3‐diisopropyltriazenide In(III) and Ga(III) precursors. Herein we report the structural and thermal properties their analogues employing combinations of isopropyl, sec‐butyl and tert‐butyltriazenide alkyl groups on the exocyclic nitrogen of the triazenide ligand. The new triazenide compounds were all found to be volatile (80‐120 °C, 0.5 mbar) and showed very good thermal stability (200 and 300 °C). These new triazenide analogues provide a set of precursors whose thermal properties are determined and can be accordingly tailored by strategic choice of exocyclic nitrogen alkyl substituents.

Palladium‐catalyzed CH acetoxylation of arenes using a pyrazolonaphthyridine ligand

AbstractHerein, Pd‐catalyzed CH acetoxylation reactions of arenes are developed using a pyrazolonaphthyridine ligand. In the presence of iodomesitylene diacetate as the oxidant, the electron‐deficient ligand facilitates the CH activation of the electron‐rich positions while preventing the formation of Pd black via bidentate binding. Although both acetic acid and hexafluoroisopropanol are employed for directing group‐assisted acetoxylation reactions, the latter proved to be more efficient for the nondirected reaction of arenes with the nitrogen ligand.

Methane partial oxidation by monomeric Cu active center confined on ZIF-7

The monomeric cupric ion (Cu2+) species coordinated to four nitrogen ligands (CuN4) is recognized as a possible active site for particulate methane monooxygenase (pMMO) of the methanotrophic bacteria that convert methane to methanol. Herein, inspired by the active site of pMMO, a copper-doped zeolitic imidazolate framework-7 (Cu/ZIF-7) was prepared, the mononuclear CuN4 centers of which displayed catalytic partial oxidative activity and converted methane to methanol, methyl hydroperoxide, and hydroxymethyl hydroperoxide without producing the overoxidized product of formic acid. Spectroscopy studies established the mononuclear Cu2+ center coordinates with four benzimidazole nitrogens. The catalytic activity of Cu/ZIF-7 was scrutinized considering the potential reaction mechanism at the CuN4 center, which substantially reduced the strong acidity of ZIF-7 to afford the partial oxidation of methane without forming formic acid.

Synthesis, characterization and anticancer activities of cationic η6-p-cymene ruthenium(II) complexes containing phosphine and nitrogenous ligands

Ruthenium-based anticancer agents have created a center of attention in the field of inorganic medicinal chemistry. The first fully characterized cationic ruthenium(II)-arene complexes [Ru( η 6 -p- cymene) (PAr 3 )L N Cl] + with highly lipophilic PAr 3 ligands where Ar = 3,5-((CH 3 ) 3 C) 2 C 6 H 3 – ( L1 ), 3,5-(CH 3 ) 2 C 6 H 3 – ( L2 ), 4-CH 3 O-3,5-(CH 3 ) 2 C 6 H 2 – ( L3 ) and 4-CH 3 O-C 6 H 4 – ( L4 ) with N = 3-methylpyridine ( 1 – 4 , respectively), or L4 and 4-methylpyridine ( 5 ), or L4 and CH 3 CN ( 6 ) were obtained (yields 67–91%) as solids stable to light and air. Electrical conductance indicates that all the complexes are 1:1 electrolytes in solution. Their composition and purity have been unambiguously established by single-crystal X-ray diffraction, NMR spectroscopy and elemental analysis. The coordination geometries are uniform for all six complexes and each structure consist of a unipositive complex cation bearing the phosphine ligands L1 - L4 and L N = 3-methylpyridine, 4-methylpyridine or CH 3 CN attached to the organometallic fragment. The equivalent unit cell volumes per formula unit decrease with 1 > 3 > 2 > 4 > 5 > 6 , accurately reflecting the decreasing sizes of the phosphines L1 - L4 , and a greater occupied volume for 3-methyl- vs. 4-methylpyridine, and the smallest volume contribution from CH 3 CN. Electrochemical studies showed mixed electrochemical mechanisms (EC/ECE) from partial substitution of p -cymene by CH 3 CN ligands from the solvent. A large electrochemical stability window (>2.2 V) for Ru(II) was observed extending beyond the physiological E° range. The complexes were cytotoxic against human cancer cell lines in vitro , and some complexes altered cell morphology.

Homodimerization Counteracts the Detrimental Effect of Nitrogenous Heme Ligands on the Enzymatic Activity of Acanthamoeba castellanii CYP51.

Acanthamoeba castellanii is a free-living amoeba that can cause severe eye and brain infections in humans. At present, there is no uniformly effective treatment for any of these infections. However, sterol 14α-demethylases (CYP51s), heme-containing cytochrome P450 enzymes, are known to be validated drug targets in pathogenic fungi and protozoa. The catalytically active P450 form of CYP51 from A. castellanii (AcCYP51) is stabilized against conversion to the inactive P420 form by dimerization. In contrast, Naegleria fowleri CYP51 (NfCYP51) is monomeric in its active P450 and inactive P420 forms. For these two CYP51 enzymes, we have investigated the interplay between the enzyme activity and oligomerization state using steady-state and time-resolved UV-visible absorption spectroscopy. In both enzymes, the P450 → P420 transition is favored under reducing conditions. The transition is accelerated at higher pH, which excludes a protonated thiol as the proximal ligand in P420. Displacement of the proximal thiolate ligand is also promoted by adding exogenous nitrogenous ligands (N-ligands) such as imidazole, isavuconazole, and clotrimazole that bind at the opposite, distal heme side. In AcCYP51, the P450 → P420 transition is faster in the monomer than in the dimer, indicating that the dimeric assembly is critical for stabilizing thiolate coordination to the heme and thus for sustaining AcCYP51 activity. The spectroscopic experiments were complemented with size-exclusion chromatography and X-ray crystallography studies. Collectively, our results indicate that effective inactivation of the AcCYP51 function by azole drugs is due to synergistic interference with AcCYP51 dimerization and promoting irreversible displacement of the proximal heme-thiolate ligand.

Synthesis and characterization of nonlinear optical metal organic frame work – Cadmium di glycinate monohydrate

• In the polymeric structure the Cd(II) has coordinated with carboxylate oxygen atom and glycine ligand nitrogen atom. • The lattice strain was introduced by the bivalent Cadmium ion. • It shows 85% transmittance at the wavelength 425 nm • SHG efficiency is 2.08 times that of KDP crystal • It can be used as a mid-infrared (mid-IR) biosensors The new non-linear optical single crystal of Cadmium di glycinate monohydrate have been synthesized by the slow evaporation solution growth technique and it was characterized by SXRD,powderXRD,SEM, FTIR, UV-Vis-NIR, TG/DTA and SHG measurements. In the polymeric structure the metal ion Cd (II) has coordinated with carboxylate oxygen atom and glycine ligand nitrogen atom. The crystalline nature of the material was proved by PXRD pattern. The lattice strain produced by the bimetallic cadmium is found to be 0.0042. The functional groups are confirmed by FTIR analysis, again the force constant of C-C bond was enhanced to 316 Nm −1 . The UV-Visible spectrum reveals the optical qualities such as band gap, transmittance and refractive index of the grown crystal. The lower cut off wavelength was found to be 213 nm. The TG-DTA analyses were carried out to determine the thermal stability as well as the decomposition temperature. The Cadmium-Glycine frame work shows void morphology. The title compound shows superior SHG efficiency compared to standard KDP. .

Synthesis, Catalysis and Antimicrobial activity of 5d- metal chelate complex of Schiff base ligands

• An analytical technique shows that the ligand of reference (schiff base) coordinates with the central metal ion by three donating sites through azomethine nitrogen and through by two oxygen of phenolic and carboxylic group. • The spectroscopic, physical and chemical data, the square planar geometry for the Gold and tetrahedral geometry had been proposed for Iridium and Platinum chelate complexes. • The thermal data study the activation energy values have shown that metal chelate complexes have been found stable thermally. • The metal chelate complexes so for synthesized shows good antibacterial activity as compared to those of parent ligands. The metal chelates of Iridium, platinum and gold with schiff base were synthesized using metal perchlorates of the respective metal ions, and schiff base formation was done by reaction of anthranilic acid and ortho hydroxybenzaldehyde in ethanolic environment. Various analytical techniques, like, UV–Visible, FT-IR, elemental analysis, molar conductance and magnetic susceptibility have been used for crystal structural analysis. A general formula of the type [M (HL) OH] of the metal complexes have been proposed by elemental and spectral analysis. The ligand to metal ratio was found to be 1:1 in all the metal chelate complexes. As per the Infrared spectral data study the interaction of oxygen (phenolic OH and acidic COOH) and an azomethine nitrogen of ligand have been found to coordinate tridentately with central metal ion. For the synthesis of metal chelate complexes the utilized activation energy was evaluated by the broido method. The synthesized metal chelate complexes and the parent ligands were analyzed also for the antibacterial activity determination against gram positive ( B. subtilis , Bacillus anthracis ) and gram negative ( Yersinia pestis , Escherichia coli ) bacterial species.

Preparation, spectroscopic and thermal investigation of fluorinated Sm(III) β-diketonates with bidentate N donor ligands

• Heteroleptic ternary samarium complexes were synthesized. • Optical and photophysical characteristics of complexes were examined spectroscopically. • From Tauc’s relation, optical band gap was determined. • PL emission spectra evince most intense peak at 649 nm ( 4 G 5/2 → 6 H 9/2 ). • Might be suitable candidate for display applications. A series of samarium β-diketonates comprising nitrogen-heterocyclic auxiliary moiety were synthesized and characterized spectroscopically. A comprehensive analysis of complexes suggests the octacoordinated environment about samarium ion and similar structural behavior of complexes. The samarium ion is coordinated via carbonyl oxygen of diketone unit and nitrogen of neutral ligand. Energy band gap values of complexes lie in range of semiconducting materials. The photophysical properties of complexes were evaluated from photoluminescence spectra of complexes. By examining the energy transfer pathway and emission spectra, the sensitizing nature of chromophoric ligands is revealed. These synthesized complexes have shown peak around 649 nm ( 4 G 5/2 → 6 H 9/2 ) due to electric dipole transition. Results of luminescence spectra and colorimetric analysis have demonstrated the emission of synthesized samarium complexes in reddish orange region. The optical and photophysical properties of complexes claim the usefulness of prepared samarium complexes in designing display devices.

Assembly of a 3D Cobalt(II) Supramolecular Framework and Its Applications in Hydrofunctionalization of Ketones and Aldehydes

A ditopic nitrogen ligand (E)-N′-(pyridin-4-ylmethylene)isonicotinohydrazide (L) containing both divergent pyridyl coordination sites and a hydrogen-bonding hydrazide–hydrazone moiety was synthesized. The Co(NCS)2-mediated self-assembly of L has resulted in the synthesis of a novel 3-dimensional (3D) supramolecular framework (1) that features both coordination and hydrogen bonding interactions. X-ray structural analysis reveals the formation and coordination mode of 1 in the solid state. The rational utilization of coordination bonds and hydrogen bonding interactions is confirmed and responsible for constructing the 3D materials. Catalytic studies using 1 in the presence of an activator are performed for the hydroboration and hydrosilylation reactions of ketones and aldehydes, and the results are compared with previously reported cobalt-based polymeric catalysts.

Electrochemical ammonium-cation-assisted pyridylation of inert N-heterocycles via dual-proton-coupled electron transfer

SummaryA straightforward and practical strategy for pyridylation of inert N-heterocycles, enabled by ammonium cation and electrochemical, has been described. This protocol gives access to various N-fused heterocycles and bidentate nitrogen ligand compounds, through dual-proton-coupled electron transfer (PCET) and radical cross-coupling in the absence of exogenous metal and redox reagent. It features broad substrate scope, wide functional group tolerance, and easy gram-scale synthesis. Various experiments and density functional theory (DFT) calculation results show the mechanism of dual PCET followed by radical cross-coupling is the preferred pathway. Moreover, ammonium salt plays the dual role of protonation reagent and electrolyte in this conversion, and the resulting product 9-(pyridin-4-yl)acridine compound can be used for fluorescence recognition of Fe2+ and Pd2+ with high sensitivity.

Carbon materials functionalized by nitrogenous ligands for dual application in energy storage and production: Fuel cells and supercapacitors

Dual-purpose fuel cell/supercapacitor materials were made by covalent embedding of phenazin-iron adducts into various commercial carbon supports (Vulcan XC-72, Black Pearls 2000, Ketjen Black 600). The diazonium coupling reaction allows for controlled deposition of nitrogen functionalities to the carbon supports via the formation of the strong carbon-carbon bond between the nitrogenous ligand and carbon surface. The novel phenazin-functionalized carbon supports were prepared and fully characterized using thermogravimetric analysis, Raman spectroscopy, and BET pore size determination. Notably, the micro-and macrostructure and the porosity of the carbon support drastically affected the catalytic activity of the system in oxygen reduction reaction (ORR). The KB-phenazin-Fe-700 showed the highest activity for the ORR in both basic and acidic media. Interestingly, the heat treatment of the phenazin-based materials resulted in a significant increase in the ORR activity that is different from the trend we previously observed for terpyridine-based catalysts on Vulcan carbon that were demonstrating a significant decrease in the activity after heat treatment. Furthermore, the potential of the same materials to be used for energy storage was explored and their performance as supercapacitors was studied. The modification of the carbon surfaces by phenazin ligand shows significant improvement of the specific capacitance when examined in acidic media. Coordination of iron to the surface results in a further increase of the specific capacitance due to the additional Faradaic contributions. Drastic increases were seen in the capacitance when Fe was added to the BP-phenazin system. Interestingly, the heat treatment process was found to decrease the energy storage ability of the materials with a significant decrease of the specific capacitance. Thus, for phenazin-based materials, the heat treatment is a necessary step for the production of effective ORR catalysts but is undesirable for materials targeting mainly energy storage applications.

New Complexes of organotin(IV) and organosilicon(IV) with 2-{(3,4-dimethoxybenzylidene)amino}-benzenethiol: Synthesis, spectral, theoretical, antibacterial, docking studies

• Organotin(IV) and Organosilicon(IV) complexes of Schiffbase have been synthesized. • Complexes exhibited trigonal bipyramidal and octahedral geometry. • Antibacterial activity was evaluated against gram(−) and gram(+) bacterias. • [Bu 2 Sn(L) 2 ] show highest binding affinity. • Complexes and proteins interact via hydrogen-bonding and Vander Waals interactions. New series of dimethyl-, dibutyltin(IV), trimethylsilicon(IV), and phenylsilicon(IV) compounds with bidentate nitrogen and sulphur donor ligands have been synthesized with the 2-{(3,4-dimethoxybenzylidene)amino}-benzenethiol (LH), in molar ratios of 1:1 and 1:2. For structure elucidation, all produced compounds were characterized using IR, UV–vis, elemental analysis, conductance measurements, NMR ( 1 H, 13 C, 29 Si, 119 Sn) spectroscopy techniques. The 2-{(3,4-dimethoxybenzylidene)amino}-benzenethiol behaves as monofunctional bidentates, interacting with the tin and silicon atom via the thiolic-sulphur and azomethine-nitrogen atoms. Compound 1, 3, and 5 have a five-coordinated trigonal bipyramidal geometry surrounding the metal atoms, whereas Compound 2, 4, and 6 have deformed octahedral structures. The optimum geometrical parameters, including bond length, bond angles, HOMO, LUMO, electrophilicity index, chemical hardness, global softness, and mulliken atomic charges, were determined using density functional theory-based methods (DFT). The studied compounds and their ligands were simultaneously evaluated for antibacterial activity in-vitro and compared to streptomycin. The binding affinity of compound with bulky group and hydrogen bond acceptor groups is more in comparision of other compounds. The structure activity relationship revealed that compounds with bulky and hydrogen bond acceptor group will enhance the antibacterial activity agaisnt Staphylococcus aureus . Six organometallic complexes of 2-{(3,4-dimethoxybenzylidene)amino}-benzenethiol were synthesized and structurally characterized. Molecular structures showed that metal(IV) ions are chelated by ligand N,S-atoms forming a distorted trigonal bipyramidal and octahedral geometry. In-vitro antibacterial evaluation showed that, the complexes were more active the free ligand. Molecular docking studied that complexes-protein interactions are spontaneous via hydrogen bonding, vander Waals interactions.

An Alternate [2×2] Grid Constructed Around TiO4 N2 Units.

The formation of a tetranuclear self-assembled species constructed around a TiO4 N2 motif is reported. This aggregate is generated from Ti(Oi Pr)4 , 2,2'-bipyrimidine (bpym) and a bis-biphenol strand (L2 H4 ) where two 2,2'-biphenol units are connected with a biphenyl spacer. The solid-state structure of the [Ti4 (L2 )4 (bpym)4 ] architecture reveals the formation of an unprecedented chiral alternate [2×2] grid. In addition to the structural characterization of the [Ti4 (L2 )4 (bpym)4 ] architecture, geometry optimisation on various possible isomeric tetrameric assemblies ([2×2] grid, alternate [2×2] grid, circular helicate or cyclic hemihelicate) is performed using DFT calculations. These results confirm the higher stability of the alternate [2×2] grid over the other possible tetranuclear isomers and allow examining the replacement of the bpym ligands by two novel diimine chelates within the tetranuclear assembly (2,2'-bipyridine=bipy and 2,2'-bipyrazine=bipyraz). From this initial theoretical investigation, the competition between these three nitrogen ligands in the course of the self-assembly process is next evaluated. Overall, this investigation shows that the exclusive formation of the alternate [2×2] grid is driven by CH⋅⋅⋅N interactions.

Studies on the binding of nitrogenous bases to protoporphyrin IX iron(II) in aqueous solution at high pH values

Studies are reported on the formation of low-spin six-coordinate [Fe(PPIX)L2] complexes from iron(II) protoporphyrin where L is one of a series of nitrogenous ligands (aliphatic, aromatic or heterocyclic). The bonding constants have been determined by titration of the metal complex with these ligands and are compared in relation to previous studies. The adduct formation was monitored utilising optical spectroscopy. In addition, Mӧssbauer spectroscopic experiments were conducted to monitor the electronic environment around the central iron atom in these complexes. The two complementary spectroscopic methods indicated that all nitrogen ligands formed low-spin octahedral complexes. The magnitude of the overall binding constants (β2 values) are discussed and related to (a) the pKa values of the free ligands and (b) the Mössbauer parameter ΔEQ, which represents the quadrupole splitting of the haem iron. The β2 and ΔEQ values are also discussed in terms of the structure of the ligand. Cooperative binding was observed for nearly all the ligands with Hill coefficients close to 2 for iron(II) protoporphyrin; one of these ligands displayed a much greater affinity than any we previously studied, and this was a direct consequence of the structure of the ligand. Overall conclusions on these and previous studies are drawn in terms of aliphatic ligands versus aromatic ring structures and the absence or presence of sterically hindered nitrogen atoms. The implications of the work for the greater understanding of haem proteins in general and in particular how the nitrogenous ligand binding results are relevant to and aid the understanding of the binding of inhibitor molecules to the cytochrome P450 mono-oxygenases (for therapeutic purposes) are also discussed.Graphical abstractChanges in the electronic absorption spectra of five-coordinate [Fe(II)(PPIX)(2-MeIm)] that occurred as the temperature was lowered from room temperature to 78° K

Synthesis, electronic structures, and reactivity of mononuclear and dinuclear low-valent molybdenum complexes in iminopyridine and bis(imino)pyridine ligand environments

Molybdenum in redox non-innocent ligand environments features prominently in biological inorganic systems. While Holm and coworkers, along with many other researchers, have thoroughly investigated formally high-oxidation-state molybdenum (Mo(IV)-Mo(VI)) ligated by dithiolenes, less is known about molybdenum in other formal oxidation states and/or different redox-active ligand environments. This work focuses on the investigation of low-valent molybdenum in four different redox non-innocent nitrogen ligand type environments (mononucleating and dinucleating iminopyridine, mononucleating and dinucleating bis(imino)pyridine). The reaction of iminopyridine N-(2,6-diisopropylphenyl)-1-(pyridin-2-yl)methanimine (L1) with Mo(CO)3(NCMe)3 produced Mo(L1)(CO)3(NCMe). Mo(L1)(CO)3(NCMe) undergoes transformation to Mo(L1)(CO)4 upon treatment with CS2 or prolonged stirring in dichloromethane. The reaction of the open-chain dinucleating bis(iminopyridine) ligand N,N'-(2,7-di-tert-butyl-9,9-dimethyl-9H-xanthene-4,5-diyl)bis(1-(pyridin-2-yl)methanimine) (L2) similarly produced an hexacarbonyl complex Mo2(L2)(CO)6(NCMe)2 which also underwent transformation to the octacarbonyl Mo2(L2)(CO)8. Both complexes featured anti-parallel geometry of the chelating units. The oxidation of Mo(L1)(CO)3(NCMe) with I2 resulted in Mo(L1)(CO)3I2. The reaction of mononucleating potentially tridentate bis(imino)pyridine ligand (L3) (N-mesityl-1-(6-((E)-(mesitylimino)methyl)pyridin-2-yl)methanimine) with both Mo(CO)3(NCMe)3 and Mo(CO)4(NCMe)2 produced complexes Mo(L3)(CO)3(NCMe) and Mo(L3)(CO)4 in which L3 was coordinated in a bidentate fashion, with one imino sidearm unbound. The reaction of dinucleating macrocyclic di(bis(imino)pyridine) analogue (L4) led to the similar chemistry of Mo2(L4)(CO)6(NCMe)2 and Mo2(L4)(CO)8 complexes. Treatment of Mo(L3)(CO)3(NCMe) with I2 formed a mono(carbonyl) complex Mo(L3)(CO)I2 in which molybdenum was formally oxidized and L3 underwent coordination mode change to tridentate. The electronic structures of formally Mo(0) complexes in iminopyridine and bis(imino)pyridine ligand environments were investigated by density functional theory calculations.

Recent Progress in Luminescent Cu(I) Halide Complexes: A Mini-Review.

Copper(I) halide complexes are well sought-after materials due to their rich structural diversities and photophysical properties. Profoundly, there is a direct relationship between each structural variation and luminescence of these complexes, for a purported use. In this review, recent publications within the last 2 years about copper(I) halide complexes, centering on their structural dimensionalities with derivatives of nitrogen, phosphorus, and sulfur ligands, have been considered alongside their effects on luminescence.