Cr Complexes Research Articles

Synthesis, characterization, anti-microbial and thermal investigation study of Schiff base derived from 1,7,7-Trimethylbicyclo [2.2.1] heptan-2-one with 4-Hydroxyphenylalanine and its metal complexes

Synthesis of bidentate Schiff base ligand by the condensation of 1,7,7-Trimethylbicyclo [2.2.1] heptan-2-one with 4-Hydroxyphenylalanineand its complexes of Co (III), Cu (II) and Cr (III). Synthesised ligand and its complexes were characterised by FT-IR, UV- Visible spectroscopy, Gouy method, molar conductance study and thermal analysis. Spectral data shows that distorted octahedral geometry of Cobalt (III), square planar geometry of Copper (II), and octahedral geometry of Chromium (III) complexes. The thermal stability of complex is explained on the reverse order of Irving William series. All the complexes are coloured, stable in air, non-electrolytic nature and soluble in DMSO solvent. The antimicrobial activity was studied using two bacteria such as Klebsiella pneumoniae and Bacillus subtilis and two fungi such as Aspergillus Niger and Candida albicans by agar well-diffusion method. The result shows that metal complexes have higher biological activity than the ligand and the Cu (II) complex show 79.31% antibacterial activity on Bacillus subtilis.

Deep eutectic solvent decomposition-based microextraction for chromium determination in aqueous environments by atomic absorption spectrometry with electrothermal atomization.

A sensitive, rapid, and simple procedure for the determination of traces of chromium species in natural and waste waters after microextraction using a quasi-hydrophobic deep eutectic solvent based on tetrabutylammonium bromide and hexanoic acid was developed for the first time. In the developed procedure, the deep eutectic solvent played the role of a source of dispersive agent, chelating agent, and extraction solvent. During mixing the aqueous phase with the quasi-hydrophobic deep eutectic solvent, dissolution and dissociation of tetrabutylammonium bromide took place. Tetrabutylammonium bromide acted as a dispersive agent for the hexanoic acid emulsion formation and as an agent for the formation of an ion-association complex with Cr(vi) in an aqueous phase followed by its extraction in hexanoic acid. The organic phase containing Cr(vi) complexes was analyzed by atomic absorption spectrometry with electrothermal atomization. The enrichment factor value was 53, the extraction recovery was 89%, and the limit of detection calculated from a blank test, based on 3σ, was 5.0 ng L-1. The values of intra-day RSD and inter-day RSD were 3.9% and 5.0%, respectively.

Ligand control of low-frequency electron paramagnetic resonance linewidth in Cr(III) complexes.

Understanding how the ligand shell controls low-frequency electron paramagnetic resonance (EPR) spectroscopic properties of metal ions is essential if they are to be used in EPR-based bioimaging schemes. In this work, we probe how specific variations in the ligand structure impact L-band (ca. 1.3 GHz) EPR spectroscopic linewidths in the trichloride salts of five Cr(iii) complexes: [Cr(RR-dphen)3]3+ (RR-dphen = (1R,2R)-(+)-diphenylethylenediamine, 1), [Cr(en)3]3+ (en = ethylenediamine, 2), [Cr(me-en)3]3+ (me-en = 1,2-diaminopropane, 3), [Cr(tn)3]3+ (tn = 1,3-diaminopropane, 4) [Cr(trans-chxn)3]3+ (trans-chxn = trans-(±)-1,2-diaminocyclohexane, 5). Spectral broadening varies in a nonintuitive manner across the series, showing the sharpest peaks for 1 and broadest for 5. Molecular dynamics simulations provide evidence that the broadening is correlated to rigidity in the inner coordination sphere and reflected in ligand-dependent distribution of Cr-N bond distances that can be found in frozen solution.

Synthesis And Spectral Study Of Cr(Iii), Mn(Ii), Ni(Ii) And Cu(Ii) Complexes Of Schiff Base Derived From Diacetylmonoxime With Thiourea

Transition metal complexes of Cr(III), Mn(II), Ni(II) and Cu(II) of the Schiff base; 1-((2E,3E)-3-(hydroxyimino)butan-2-ylidene)thiourea were synthesized and characterized on the basis of physical characteristics, molar conductivity, micro-analytical data(CHN), magnetic moment measurements, Mass spectra, 1HNMR, IR and UV-Vis spectrum data. The elemental analysis data showed the complexes are in 1:1 [M:L] ratio. The molar conductance values revealed the complexes of Cr(III), Mn(II), Ni(II) are electrolyte in nature while the Cu(II) complex is non-electrolyte. The results of magnetic moment measurements showed that, the complexes of Cr(III), Mn(II), Ni(II) and Cu(II) have unpaired electrons. The electronic spectral results of the Schiff base ligand and its complexes suggested that, the Cr(III), Ni(II), Mn(II) and Cu(II) complexes have an octahedral structure.

Interplay of Hückel and Möbius Aromaticity in Metal-Metal Quintuple Bonded Complexes of Cr, Mo, and W with Amidinate Ligand: Ab initio DFT and Multireference Analysis*.

The aromaticity of metal-metal quintuple bonded complexes of the type M2 L2 (M=Cr, Mo, and W; L=amidinate) are studied employing gauge including magnetically induced ring current (GIMIC) analysis and electron density of delocalized bonds (EDDB). It is found that the complexes possess two types of aromaticity: i) Hückel aromaticity through delocalization of ligand π electrons with metal-metal δ-bond-forming 6 conjugated electrons (4π and 2δ) ring; ii) Craig-Möbius aromaticity through delocalization of π electrons of both the ligands with metal d-orbitals in Craig type orientation forming 10π electrons ring with a double twist. Extended transition state natural orbital chemical valence (ETS-NOCV) and canonical molecular orbital natural chemical shielding (CMO-NCS) analysis confirm the Craig-Möbius type arrangement of the orbitals. Furthermore, the unprecedented Hückel and Möbius type aromaticity is confirmed from the plot of the current pathways using 3D line integral convolution (3D-LIC) plots. The metal-metal bond order also increases down the group as justified from the complete active space self-consistent field (CASSCF) analysis. Due to an increase in the π and δ electron conjugation, both the Hückel and Möbius aromaticity increase down the group.

Synthesis, Characterization and Thermal Studies of Cr (III), Co (II) and Ni (II) Complexes with Schiff Base

The physiologically active compounds of Schiff bases find application in the treatment of several diseases. This biological activity of Schiff base is attributed to the formation of stable chelates with a transition metal, and they are known to exhibit a wide variety of pharmacological properties and carcinostatic activities. Cr (III), Co (II), and Ni (II) complexes of Schiff base were chosen for the present experimental work and theoretical treatment and characterized by different spectroscopies such as elemental analysis CHN, infrared, ultra visible spectroscopies, magnetic susceptibility, molar conductivity measurements, and thermal analysis The results of this research, indicate that the complexes have a type composition [M (NL)]. Schiff base NL: derived from 2-aminobenzoic acid and Benzil, M: Cr (III), Co (II), and Ni (II) transition metal ions. Schiff base acts as a tetradentate ligand with ions through the hydroxyl groups and imine groups. The work was included theoretical calculations of NL and its complexes, which were done by the program of hyperchem8. 0.7 using semi-empirical calculations. The PM3 method used to calculate the heat of formation (ΔH○f), binding energy (ΔEb), total energy (ΔEtot), and geometric properties of the compounds.

Synthesis and Optical Studies of the 3,4-dimethoxy Benzaldehyde [5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl]Hydrazone Metal Complexes

The aim of the present study is to synthesize and optical studies of 3,4-dimethoxy benzaldehyde [5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl]hydrazone metal complexes. Firstly, the 3,4-dimethoxybenzaldehyde [5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl] hydra zone was synthesized by the reaction of the 2-(5-hydrazino-1,3,4-oxadiazol-2-yl)phenol with 2,3-dimethoxybenzaldehyde in the ethanol as a solvent . Scondly, its complexes of Cr(III), Fe(III), Co(II) and Ni (II) have been synthesized. The synthesized coumpounds and its metal complexes were characterized by the FTIR, Mass spectra and UV-vis absorption. The results confirmed the suggested square planar geometry of the Ni (II) complex and tetrahedral geometry of the Co(II) complex, while Cr (III), Fe(III) complexes were assigned octahedral geometrics. The optical absorption spectra of those complexes in the wavelength range from 200-900 nm were studied.The results showed that the optical absorption is due to indirect allowed transitions of the compound and its complexes, the energy gap (Eg) of these compounds decreases in the order L> Ni (II)> Fe(III)> Co(II) and > Cr(III), the absorption coefficient (α), real and imaginary parts (ɛr,ɛi), and optical conductivity (σopt)were estimated.

Synthesis and Optical Studies of the 3,4-dimethoxy Benzaldehyde [5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl]Hydrazone Metal Complexes

The aim of the present study is to synthesize and optical studies of 3,4-dimethoxy benzaldehyde [5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl]hydrazone metal complexes. Firstly, the 3,4-dimethoxybenzaldehyde [5-(2-hydroxyphenyl)-1,3,4-oxadiazol-2-yl] hydra zone was synthesized by the reaction of the 2-(5-hydrazino-1,3,4-oxadiazol-2-yl)phenol with 2,3-dimethoxybenzaldehyde in the ethanol as a solvent . Scondly, its complexes of Cr(III), Fe(III), Co(II) and Ni (II) have been synthesized. The synthesized coumpounds and its metal complexes were characterized by the FTIR, Mass spectra and UV-vis absorption. The results confirmed the suggested square planar geometry of the Ni (II) complex and tetrahedral geometry of the Co(II) complex, while Cr (III), Fe(III) complexes were assigned octahedral geometrics. The optical absorption spectra of those complexes in the wavelength range from 200-900 nm were studied.The results showed that the optical absorption is due to indirect allowed transitions of the compound and its complexes, the energy gap (Eg) of these compounds decreases in the order L> Ni (II)> Fe(III)> Co(II) and > Cr(III), the absorption coefficient (α), real and imaginary parts (ɛr,ɛi), and optical conductivity (σopt)were estimated.

Synthesis of Binuclear Complexes of Cu (II), Ni (II) and Cr (III) Metal Ions Derived from Di-Imine Compound as Biterminal Binding Site Ligand

The research is concerning synthesis of two di-imine ligands derived from thiadiazole heterocyclic compounds. 1, 3, 4-thiadiazole-2, 5-dihydrazino is considered as ligand (L1) and starting essential compound that used as precursor to synthesize the new ligand (2, 2'-(((1,3,4-thiadiazole-2,5-diyl)bis(hydrazin-2yl1ylidene))bis (methaneylylide)) diphenol (L2). Six new complexes were derived from the ligands using some transition metal ions like Cu(II), Ni(II), and Cr(III).The synthesized compounds characterized by infra-red, ultra-violet-visible and gas chromatography-mass spectroscopy, conductivity, and thermal analysis. The coordination modes were suggested to be N2from two terminals to form binuclear complexes. The mentioned characterization methods showed that the prepared complexes may have chelation pattern (bidentate or tridentate) depending on the suggested geometry (square planer or octahedral) and the type of ligand.

Selective synthesis of mono(amidinate) chromium(II) chloride complexes and a computational insight of their interaction with human insulin

Treatment of one equivalent of sterically bulky lithiated amidinate ligands, [RC(NHAr)(NAr)] {R = Ph and Ar = 2,6-diisopropylphenyl (1); R = t-Bu and Ar = 2,6-diisopropylphenyl (2)}, with anhydrous chromium(II) chloride in tetrahydrofuran (THF) afforded, after workup in pentane or hexane, selectively rare examples of mono(amidinate) Cr(II) complexes, [{PhC(NAr)2}Cr(µ-Cl)(thf)]2 (3) and [{t-BuC(NAr)2}Cr(µ-Cl)]2 (4) in 48 and 45% yields, respectively. X-ray analysis shows both 3 and 4 to be dimeric with the amidinate ligands η2-coordinated to one Cr atom each and the Cl ligands bridge the two Cr centers. Owing to the low steric bulk of the amidinate ligand in 3, one thf ligand is coordinated to each Cr atom. A sterically less bulky ligand, [RC(NHAr)(NAr)] {R = t-Bu and Ar = 2,6-dimethylphenyl (5)} instead led to a bis(amidinate) Cr(II) complex (6). A molecular docking simulation of the ligands and metal ligated complexes was performed with the human insulin protein (PDB code: 3Q6E.) to gauge the potential of the metal complexes as effective drug candidates for the treatment of type I and type II diabetes. Docking simulations of the ligands and metal complexes showed a strong binding inside the active site cleft. The docked poses showed important binding features, mostly because of the interactions due to the aromatic moieties of the amidinate ligands.

Synthesis, Characterization, and Catalytic Activity of Bimetallic Ti/Cr Complexes

We report herein the reactions of the Rosenthal complexes, Cp2Ti(BTMSA) and Cp*2Ti(BTMSA) (BTMSA: bis(trimethylsilyl)acetylene), with CpCr(CO)3H. Those complexes are known to dissociate their alkyne ligands and to exhibit the reactivities of the putative titanocenes “Cp2Ti” and “Cp*2Ti”. Our reactions appear to proceed through the addition of CpCr(CO)3H to these titanocenes, giving rise to TiIV-H intermediates that lose H2 to form the TiIII–Cr complexes 1 and 2. In the solid state, 1 and 2 both adopt a dimeric geometry, involving a 12-membered “Ti2Cr2” ring held together with Ti–O–C–Cr bridging carbonyls. The terminal carbonyls in 1 and 2 are trans. DFT calculations confirm that the loss of H2 from the TiIV-H intermediate—forming the TiIII-Cr dimer—is exergonic by 14.2 kcal mol–1 in the gas phase. The Bercaw compound Cp* (C5Me4CH2)TiCH3 reacts with CpCr(CO)3H to form a TiIV-CH3 species with a coordinated CpCr(CO)3– anion (3). The Ti-Cr dimer 1 is capable of catalyzing the hydrogenation of an epoxide to an anti-Markovnikov alcohol, avoiding the use of Cp2TiX2 (X = Cl– or mesylate), NaCpCr(CO)3, and HCpCr(CO)3 separately as in our previous catalyst system.

Mixed Ligand Complexes of Schiff Base and Nicotinamide: Synthesis, Characterization and Antimicrobial Activities

A new Schiff base of HL has been synthesized from amoxicillin drug and 4-Chlorobenzophenone. Cr (III), Fe (III), Co (II), Ni (II), Cu (II), Cd (II) and Hg (II) mixed ligands complexes of Schiff base and Nicotinamide. Diagnosis of synthesis ligand and its complexes are done by1HNMR, 13CNMR and thermal analysis for HL ligand, FTIR, UV-visible, molar conductance, CHN analysis, magnetic susceptility and atomic absorption. Octahedral geometries have been suggested for all complexes. All compounds under study were tested antimicrobial activity against four type of bacteria such as Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus Bacillis subtilis in nutrient agar.

Semi-aromatic polyester synthesis via alternating ring-opening copolymerization using a chromium complex based on a pentapyridine ligand

The present study examined the use of a Cr(III) complex bearing a pentapyridine ligand as a catalyst in alternating ring-opening copolymerization (ROCOP) to prepare polyesters. Alternating ROCOP of anhydride (phthalic anhydride or 1,8-naphthalic anhydride) and cyclic epoxide (cyclohexene oxide) was performed using a Cr(III) pentapyridine complex (1) and a cocatalyst, DMAP (4-dimethylaminopyridine) or PPNCl ((bis(triphenylphosphine)iminium chloride). After optimizing the monomer ratio and reaction conditions, fully alternating polyesters with narrow polydispersity were synthesized (Mn up to 10.4 kg/mol, Ð below 1.3). These results demonstrate that Cr(III)-based catalysts bearing pentapyridine ligands can generate fully alternating polyesters.

New metal complexes of sulfonamide: Synthesis, characterization, in‐vitro anticancer, anticholinesterase, antioxidant, and antibacterial studies

In this research work a sulfonamide from tranexamic acid has been synthesized followed by its metal complexation. p‐Bromo benzene sulfonyl chloride was used to synthesize sulfonamide using eco‐friendly atmosphere. The sulfonamide prepared from tranexamic acid has been utilized for the preparation of metal complexes with various metals like Ni, Cu, Co, Mn, Pb, Cd, Cr, Fe, Sn, and Sr. All synthesized compounds were characterized by applying different spectral techniques such as Fourier‐transform infrared (FTIR), mass spectrometry, and X‐ray diffraction (XRD) analysis. The biological activities such as radical scavenging activity, enzyme inhibition, antifungal, antibacterial, and anticancer were performed. It was concluded from the results that compounds showed moderate to good activity. Cu complex of sulfonamide showed the highest antioxidant potential (87.69 ± 1.8% with IC50 137 ± 1.0 μg) while Cr complex depicted the highest activity against both enzymes; AChE (73.51 ± 1.7% with IC50 165 ± 1.1 μg) and BChE (70.05 ± 1.3% with IC50 152 ± 1.8 μg). Mn complex showed good results against six bacterial strains comparable with standard drug. Cr complex depicted highest anticancer activity against MCF7 and human corneal epithelial cell (HCEC) cell lines 45.73% and 25.40%, respectively. These results concluded that metal complexes of sulfonamide may be good induction in the future for medical purposes.

Synthesis of Sulfur-rich Polymers: Copolymerization of Cyclohexene Sulfide and Carbon Disulfide Using Chromium Complexes

An investigation of the copolymerization of cyclohexene sulfide and carbon disulfide using salphen and salen Cr complexes as catalysts and [PPN]+X– salts as cocatalysts, at different temperatures and reaction times, is reported. Both catalytic systems produce both polymer and cyclic products. For the first time, poly(trithiocyclohexylcarbonates) (PCS) have been synthetized in high yields and high molecular weights. Salphen-based catalysts, in comparison with salen-based ones, show higher productivity and selectivity for polymers with high molecular weight up to 18 kg/mol when the reaction is carried out at 25 °C. At a higher temperature with (salphen)CrCl, the maximum value of selectivity for copolymers (72%) was obtained at a short reaction time (3 h). At long reaction times, great amounts of cyclic by-product are observed, thus evidencing the tendency for cyclohexene sulfide and CS2 to provide cyclic products due to the stability of the trithiocyclohexylcarbonate. PCS possesses high refractive index (n > 1.72), and antimicrobial assays reveal that these materials are active against Escherichia coli and moderately active against Staphylococcus aureus. These properties along with the Tg values of 80 °C make these polymers suitable for interesting applications different from those of poly(trithiopropylencarbonate).

Synthesis, characterization, thermal, DFT computational studies and anticancer activity of furfural-type schiff base complexes

Novel Schiff base ligand N1,N2-bis(furan-2-ylmethylene)-4-methylbenzene-1,2-diamine (L) has been synthesized. The metal complexes of L with metal ions of silver (I), chromium (III), iron (III), cobalt (II), copper (II), cadmium (II), mercury (II), and uranium (VI) were investigated using various spectroscopic techniques (FT-IR, 1H NMR, UV, mass), elemental analysis, TGA, conductivity, X-ray diffraction, fluorescence, and magnetic susceptibility measurements. The conductivity measurements showed the electrolytic nature of the complexes except for Co(II), Cu(II), and Hg(II) complexes. Octahedral geometry was proposed for all complexes except Ag(I) complex that was observed as tetrahedral geometry based on the magnetic moment and spectral studies. The values of optical band gap energy (Eg) of the synthesized complexes and CdO (1.83–3.44 eV) suggested that these compounds could be used as semiconductors. The X-ray diffraction patterns of Schiff base and its complexes were investigated and nano-crystalline size was established for Ag(I), Cr(III), Fe(III), Co(II), Cu(II), and Cd(II) complexes. Theoretical calculations were carried out for the determination of the optimization geometry, vibrational frequencies, energy of HOMO and LUMO as well as the quantum chemical parameters for ligand and its Ag(I), Cr(III), Fe(III), Co(II), Cu(II) and Cd(II) complexes. Furthermore, the photocatalytic properties of the synthesized Fe2O3, Co3O4, CuO, and CdO nanoparticles for degradation of the methylene blue (MB) have been examined. The results showed that combined of H2O2 with catalyst increased the percent of degradation of MB to 83.29, 60.71, 73.70, and 77.24% in 90 min for the nanoparticles Fe2O3 (24 nm), Co3O4 (30 nm), CuO (35 nm), and CdO (74 nm), respectively, which is consistent with particle size. Antimicrobial screening confirmed that Cd(II) complex exhibited greater activity than both ligand and Gentamicin, the reference drug against both Gram-positive and E. coli bacterial strains. In addition, the Hg(II) complex displayed higher activity than both ligand and standard Ketoconazole against fungi. The cytotoxicity of the Cd(II) complex on Human liver carcinoma (Hep-G2) cells showed the highest potent cytotoxicity effect against the growth of carcinoma cells compared to the Vinblastine standard and the ligand.

Synthesis, Physico-Chemical Characterization and Antibacterial Studies of New Fe(III) and Cr(III) Complexes with an Ionic Liquid-Supported Schiff base ligand

An ionic liquid-supported Schiff base 1-{2-(2-hydroxy-5-bromobenzylamine) ethyl}-3-ethylimidazolium tetrafluoroborate and its Fe(III) and Cr(III) complexes were prepared and characterized by various analytical and spectroscopic methods such as elemental analysis, UV-Visible, FT-IR, 1 H NMR, Mass-spectra, TGA/DTG, molar conductance and magnetic susceptibility measurements. Based on these spectral studies octahedral geometry was proposed for the both complexes. Molar conductance of the complexes showed their electrolytic nature. The Schiff base ligand and its complexes were tested for in vitro antibacterial activities against gram positive and gram negative bacteria to assess their inhibition potentials. Cr(III) complex showed higher activity than the Fe(III) complex against the tested bacteria S. aureus and E.coli.

Synthesis, characterization and cytotoxic activity study of Cu (II), Co (II), Mn (II), Ni (II) and Cr (III) Metal Complexes with new guanidine Schiff base against the hepatocellular Carcinoma (HCAM) cancer cell

In this research, a new guanidine ligand was synthesized from the condensation reaction of 1,2-hydrazinedicarboximidamide and indol-3-carboxaldehyde and its derived metal transition complexes of Co (II), Ni (II), Mn (II), Cu (II) and Cr (III) have been synthesized by reaction of metal chlorides with guanidine ligand in the molar ratio 2:1 (M:L). The guanidine ligand and its metal complexes were characterized by different spectroscopic and analytical techniques, these studies result suggests that the metal complexes have tetrahedral geometry. The cytotoxic activity of the guanidine Schiff base and its metal complexes were studied on hepatoma cellular carcinoma (HCAM) cell line.

New insights in the slow ligand exchange reaction between Cr(III)-EDTA and Fe(III), and direct analysis of free and complexed EDTA in tannery wastewaters by liquid chromatography - Tandem mass spectrometry

EDTA and soluble Cr(III) are usually both present in wastewaters coming from treatment plants handling tannery effluents. A well-established method to determine EDTA is based on the conversion of free and complexed EDTA into its Fe(III) complex. This procedure gives inconsistent data when Cr(III)-EDTA is present. This fact was here demonstrated by studying the kinetics of the exchange reaction between Fe(III) and Cr(III)-EDTA at 90 °C and various pH values, from acidic to neutral. The reaction is very slow (several weeks); the slow kinetics of conversion of Cr(III)-EDTA to Fe(III)-EDTA is even more accentuated at room temperature and the low concentrations of reactants in wastewaters. The presence of EDTA complexes of Fe(III) and Cr(III) was demonstrated in industrial effluents and wastewaters by developing a selective method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS), which was able to detect free and complexed EDTA at concentration levels <1 μM. A systematic underestimation of the EDTA expressed as Fe(III) complex was demonstrated in samples containing Cr(III)-EDTA. Cr(III)-EDTA was identified for the first time as a component of wastewater samples at a concentration level of about 2 μM and turned out to be an inert species that significantly contributes to the final soluble Cr amount. This study gives new insights into the inertness of Cr(III) toward metal exchange equilibria of EDTA complexes, resolves a bias in the analysis of total EDTA in samples containing Cr(III)-EDTA, allowing the direct determination of free and complexed EDTA by LC-MS.

Electroplating of Thick Hard Chromium Coating from a Trivalent Chromium Bath Containing a Ternary Complexing Agent: A Methodological and Mechanistic Study

Trivalent chromium electroplating is considered a greener alternative to hexavalent chromium electroplating. However, the electrochemical reduction of Cr(III) in aqueous solution is extremely unstable and the thickness of the coating can hardly grow beyond 10 μm, which limits its industrial applications. We herein report a trivalent chromium bath containing a ternary complexing agent, which yields bright and uniform chromium coatings with thickness exceeding 30 μm, as well as high hardness and corrosion resistance. The electroplating behaviors and first principal calculations reveal that the Cr(II) intermediate plays a vital role in sustained electroplating in Cr(III) baths. The composition of complexing agents has a profound effect on the geometry and electron accepting ability of the Cr(II) complex ions. The failure to grow thick Cr coating is attributed to the accumulation of inactive hydroxo-bridged complexes. In the bath with ternary complexing agent, the Cr(II) complex ions are dsp3 or dsp2 hybridized with high electron affinity, which can be readily reduced to metallic Cr. The bath also shows a strong competitive ligand-binding effect that renders Cr(II) to preferentially bind with an organic ligand rather than a hydroxy ligand. Furthermore, the planar geometry of dsp2 hybridization does not favor the formation of hydroxo-bridged complexes because of the steric hindrance effect. The above merits of the ternary complexing agent lead to sustained electroplating, and thick Cr coatings are obtained.