Silicon Complexes Research Articles

Synthesis and characterization of newly phthalocyanine molecules: Their enzyme inhibition and antioxidant properties, in silico and in vitro

Pcs exhibiting maximum absorption in the phototherapeutic window continue to shine as a beacon of hope in the treatment of cancer. In particular, they maintain skin sensitivity after treatment and can treat deep-seated tumors by stimulating them with broad-spectrum radiation. This makes them advantageous compared to their counterparts. In this study, Novel 1,2,3-triazole schiff base (5a), its methoxy homolog (5b), and their silicon complexes (SiPc-6a and SiPc-6b) were synthesized. Their proposed structures were confirmed by FT-IR, NMR, UV–vis and MS instrumental techniques. Compound (6b) showed inhibitory activity on amylase and glucosidase enzymes. Moreover, considering the glucosidase activity, compound (6b) (IC50, 22.4 ± 1.0 µM) was observed to be more effective than the standard compound (IC50, 186.1 ± 5.8 µM). Molecular docking studies showed that the synthesized compounds bind to the same enzymes with high affinity. The binding energy of SiPc-6a compound with α-amylase, α-glucosidase and tyrosinase enzymes are -10.28, -11.31 and -11.9 kcal/mol, respectively. And another compound, SiPc-6b, has a binding energy of -11.46, -10.11 and -10.27 kcal/mol with a-amylase, a-glucosidase and tyrosinase enzymes, respectively. Based on experimental results that support each other with binding energy values in quality and quantity indicating efficient binding, it is concluded that these compounds can be used in candidate drug discovery. Beside these, as a result of the studies, it was understood that all molecules have antioxidant activity. Additionally, molecular electrostatic potentials, frontier orbital analysis, natural bond orbital (NBO) properties of compounds calculated with DFT and TD-DFT methods and these properties associated with structural properties.

Size-tunable silicon nanoparticles synthesized in solution via a redox reaction.

A current challenge in silicon chemistry is to perform liquid-phase synthesis of silicon nanoparticles, which would permit the use of colloidal synthesis techniques to control size and shape. Herein we show how silicon nanoparticles were synthesized at ambient temperature and pressure in organic solvents through a redox reaction. Specifically, a hexacoordinated silicon complex, bis(N,N'-diisopropylbutylamidinato)dichlorosilane, was reduced by a silicon Zintl phase, sodium silicide (Na4Si4). The resulting silicon nanoparticles were crystalline with sizes tuned from a median particle diameter of 15 nm to 45 nm depending on the solvent. Photoluminescence measurements performed on colloidal suspensions of the 45 nm diameter silicon nanoparticles indicated a blue emission signal, attributed to the partial oxidation of the Si nanocrystals or to the presence of nitrogen impurities.

High Carbon Doping of Amorphous Silicon Nanoparticles in a One-Step Gas-Phase Process for Increased Cycling Stability

Silicon as an anode material for Lithium-Ion-Batteries (LIB) is a promising candidate to increase overall specific energy of batteries in comparison to state-of-the-art graphite anodes. Yet the cycling stability of silicon-based electrodes is still an issue, mainly due to problems related to the swelling of silicon during lithiation to up to 300 % of its original volume. While a breakage of silicon particles can be prevented by choosing a nano-material this has the detrimental effect of increasing the surface exposed to the electrolyte, i.e. reducing coulombic efficiency. Other solutions like coatings of silicon particles and complex electrode structures are shown to increase cycling stability, but are typically connected to higher manufacturing cost.By doping silicon nanoparticles already during production in a gas-phase one-step process, this study investigates the influence of high carbon concentrations up to 20 wt.%. This causes the silicon to stay amorphous, even at elevated temperatures. Furthermore it is shown, that the disturbance of the lattice by carbon atoms helps mitigating stress during lithiation, and can form a less reactive surface. By varying precursor concentrations during material synthesis, a range of materials were produced and analyzed physicochemically and electrochemically. For carbon values up to 15 wt.% our results show a strong increase in cycling stability of up to 80 % capacity retention after 500 cycles, and first cycle coulombic efficiencies of 80 – 90 %. Yet the increased stability is going along with a decrease in specific capacities to 1000 – 1500 mAh/g. These values were obtained for a 75 wt.% silicon, 15 % PAA, 10% C65 electrode and 1 mg/cm2, tested against lithium at 0.5 C. By linking further electrochemical results to particle properties the effects of the carbon doping are further unravelled. This material engineering offers another promising pathway to increase overall performance of silicon containing LIBs and is industrially viable, due to its inclusion in a scalable one-step material synthesis process. Figure 1

The Hexacoordinate Si Complex SiCl4(4-Azidopyridine)2—Crystallographic Characterization of Two Conformers and Probing the Influence of SiCl4-Complexation on a Click Reaction with Phenylacetylene

4-Azidopyridine (1) and SiCl4 react with the formation of the hexacoordinate silicon complex SiCl4(4-azidopyridine)2 (2). Upon dissolving in warm chloroform, the complex dissociates into the constituents 1 and SiCl4 and forms back upon cooling. Depending on the cooling, two different crystalline modifications of 2 were obtained, which feature two different trans-conformers. Slow cooling to room temperature afforded conformer 2′, which features coplanar pyridine rings. Rapid cooling to −39 °C afforded crystals of conformer 2″, in which the planes of the pyridine ligands are nearly orthogonal to one another. Whereas 2′ resembles the molecular arrangement of various other known SiX4(pyridine)2 (X = halide) complexes, 2″ represents the first crystallographically confirmed example of a SiX4(pyridine)2 complex in this conformation. Conformers 2′ and 2″ were studied with 13C and 29Si solid state NMR spectroscopy. Their differences in 29Si chemical shift anisotropy, as well as energetic differences, were further investigated with computational analyses. In spite of the similar stabilities of the two conformers as isolated molecules, the crystal packing of 2″ is less stable, and its crystallization is interpreted as a kinetically controlled effect of seed formation. (3+2)-cycloaddition of 1 and phenylacetylene in toluene at 110 °C yields a mixture of 1-(4-pyridyl)-4-phenyl-1,2,3-triazole (1,4-3) and 1-(4-pyridyl)-5-phenyl-1,2,3-triazole (1,5-3) in approximate 1:2 molar ratio. The crystal structures of the two isomers were determined via X-ray diffraction. In chloroform (at 60 °C), this reaction is slow (less than 2% conversion within 4 h), but the presence of SiCl4 enhanced the rate of the reaction slightly, and it shifted the triazole isomer ratio to ca. 1:6 in favor of 1,5-3.

A Review of the Synthesis, Spectral Aspects, and Biological Evaluation of Silicon(IV) Complexes with N, O, and S Donor Ligands

A Review of the Synthesis, Spectral Aspects, and Biological Evaluation of Silicon(IV) Complexes with N, O, and S Donor Ligands

Lewis Acid-Base Adducts of α-Amino Acid-Derived Silaheterocycles and N-Methylimidazole

In chloroform solution, the reaction of bis(tert-butylamino)dimethylsilane ((tBuNH)2SiMe2) and an α-amino acid (α-amino isobutyric acid, H2Aib; D-phenylglycine, H2Phg; L-valine, H2Val) in the presence of N-methylimidazole (NMI) gave rise to the formation of the pentacoordinate silicon complexes (Aib)SiMe2-NMI, (Phg)SiMe2-NMI and (Val)SiMe2-NMI, respectively. Therein, the amino acid building block was a di-anionic bidentate chelator at the silicon atom. In solution, the complexes were involved in rapid coordination–dissociation equilibria between the pentacoordinate Si complex (e.g., (Aib)SiMe2-NMI) and its constituents NMI and a five-membered silaheterocycle (e.g., (Aib)SiMe2), as shown by 29Si NMR spectroscopy. The energetics of the Lewis acid-base adduct formation and the competing solvation of the NMI molecule by chloroform were assessed with the aid of computational methods. In CDCl3 solution, deuteration of the silaheterocycle NH group proceeded rapidly, with more than 50% conversion within two days. Upon cooling to −44 °C, the chloroform solvates of the adducts (Aib)SiMe2-NMI and (Phg)SiMe2-NMI crystallized from their parent solutions and allowed for their single-crystal X-ray diffraction analyses. In both cases, the Si atom was situated in a distorted trigonal bipyramidal coordination sphere with equatorial Si–C bonds and an equatorial Si–N bond (the one of the silaheterocycle). The axial positions were occupied by a carboxylate O atom of the silaheterocycle and the NMI ligand’s donor-N-atom.

Synthesis and Crystal Structure of Dimethyl{N-[(2-oxy-1-naphthyl)methylene]leucinato}silicon

The title compound was prepared by reaction of the Schiff base ligand N-(2-hydroxy-1-naphthylidene)leucine with dichlorodimethylsilane in the presence of triethylamine as base. The resulting pentacoordinate silicon complex was characterized by NMR, IR, UV-Vis spectroscopy and melting point. The structure was confirmed by single-crystal X-ray diffraction data. It crystallizes in the monoclinic space group Ic with unit cell dimensions a = 7.2030(6), b = 22.9842(14), c = 10.8946(12) Å, β = 96.141(7)°, V = 1793.3(3) Å3, Z = 4.

Pd–Si complexes of the type ClPd(μ2-pyO)4SiR (R = Me, Ph, Bn, Allyl, κO-(pyO)PdCl(η3-allyl); pyO = pyridine-2-olate): The influence of substituent R on the Pd–Si bond

The reactions of organosiliconpyridine-2-olates (pyridyl-2-oxysilanes) RSi(pyO)3 (pyO = pyridine-2-olate, R = Me (1a), Ph (1b), Bn (1c) and Allyl (1d)) and [PdCl2(NCMe)2] in chloroform afforded the hexacoordinate silicon complexes RSi(μ2-pyO)4PdCl (R = Me (2a), Ph (2b), Bn (2c) and Allyl (2d), respectively), which feature a Pd–Si bond, in which the Pd atom is the formal lone pair donor toward Si. The new compounds 2b, 2c, 2d were characterized with multi-nuclear NMR spectroscopy and elemental analysis. The effect of the Si-bound substituent R on the trans-disposed Pd–Si bond was studied by single-crystal X-ray diffraction and computational analyses (e.g., Natural Localized Molecular Orbitals, NLMO; topological analyses of the electron density at the bond critical point with Quantum Theory of Atoms-In-Molecules, QTAIM). A structurally related byproduct, (η3-allyl)ClPd(pyO)Si(μ2-pyO)4PdCl 2d’, which formed along with target product 2d and features an Si–O bond trans to Pd–Si, was included in this systematic study. Another byproduct from the synthesis of 2d, the pentanuclear complex ClPd(μ2-pyO)2Si(μ2-pyO)2Pd(μ2-pyO)2Si(μ2-pyO)2PdCl (compound 3) was characterized crystallographically. This compound features pentacoordinate Si atoms within trigonal–bipyramidal Si(O4Pd) coordination spheres with equatorial Pd–Si bonds to the terminal Pd atoms. The Pd–Si bond situation in this compound was elucidated with the aid of computational analyses. QTAIM analyses of 3 in conjunction with a model compound PdSi4, which features two silyl groups and two silylene ligands, indicate topological properties of the electron density at the Pd–Si bond critical point which are similar to Pd–Si bonds of silyl and silylene compounds. The latter exhibit greater similarity, which indicates features of a Pd←Si bond. In contrast, NLMO analyses of 3 identify a polar covalent Pd–Si bond with predominant Pd contribution (formal Pd→Si donation).

Theoretical Study of Charge Mobility Properties of Complexes Si(DPP)(CH3)2 and Si(Bzimpy)(CH3)2

The direction of organic electronics research is attracting more and more interest from the scientific community. One of the indicators of such interest is the appearance of commercially available products with screens based on organic compounds. Therefore, conducting experimental and theoretical research in this area is an urgent task. Pentacoordination neutral complexes of silicon are poorly studied from the point of view of application in organic electronics, as well as six-coordination analogues. We present data on the calculation of reorganization energies, intermolecular transfer integrals, transfer rates and charge mobility for the optimized structures of pentacoordinated silicon complexes Si(DPP)(CH3)2 and Si(bzimpy)(CH3)2. We have applied Marcus-Hush model for calculation of charge mobilities. The Si(DPP)(CH3)2 structure contains one diphenylpyridine (DPP = 2,6-diphenylperidine) ligand. The Si(bzimpy)(CH3)2 structure contains one benzimidazole (bzimpy = 2,6-bis(benzimidazole-2'-il)pyridine) ligand. Computational data were obtained using the B3LYP hybrid functional and the basis set 6-31G*. All calculations were performed using Gaussian09 program package. The charge mobility data obtained for Si(DPP)(CH3)2 and Si(bzimpy)(CH3)2 pentacoordinated silicon complexes were compared with their six-coordinate counterparts Si(DPP)2 and Si(bzimpy)2 for which experimental data on charge mobilities become available last years. Comparison with six-coordination analogues of complexes showed that penta-coordination complexes Si(DPP)(CH3)2 and Si(bzimpy)(CH3)2 have much higher mobility of electrons, while Si(bzimpy)(CH3)2 also has higher hole mobility. We suppose this could be related to different symmetry of the pentacoordinated and hexacoordinted complexes. It is shown that the mobility of holes is much higher in the complex Si(bzimpy)(CH3)2 than in Si(DPP)(CH3)2.

Synthesis, spectral, antibacterial and QSAR studies of tin and silicon complexes with Schiff base of amino acids

A series of main group metal and metalloid complexes of Sn(IV), Sn(II), and Si(IV) ions with bidentate Schif bases derived from condensation of animo acids (Tryptophan, Histidine, Alanine, Serine, Aspartic acid) and 4‑methoxy-benzaldehyde were synthesized and were well characterized by diferent analytical and spectroscopic (UV–Vis, FT-IR, and NMR) methods, molar conductance determinations, and elemental analysis. Spectroscopic evidence indicates that Schif bases coordinate via η2-N,O-donor atoms with tin and silicon centres in a 2:1 molar ratio, with a trigonal bipyramidal and octahedral geometrical arrangement for Si(IV) and Sn(IV), respectively, and a distrtorted tetrahedral structure for Sn(II) complexes. The antibacterial efficacy of the produced compounds was tested in vitro using four different gramme (+) and gramme (-) bacteria. The designed model produced statistically significant results with of R2 = 0.93, Q2= 0.0.87 and Rpred2 = 0.92. Most potent compound forms the hydrogen bond with most active amino acids Arg136 and Gly63. The R3Sn(IV) compounds were shown to be the most effective antibacterial agent among all the produced compounds confirmed by molecular docking. The findings imply that these compounds might serve as leading compounds in the quest for novel antibacterial agents.

Influence of ratio of silicon complex and coagulant on silicon dioxide physicochemical characteristics

Influence of ratio of silicon complex and coagulant on silicon dioxide physicochemical characteristics

{N-[(4-Meth-oxy-2-oxidophen-yl)(phen-yl)methyl-idene]glycinato}di-phenyl-silicon(IV).

The title compound, C28H23NO4Si, crystallizes in the monoclinic space group P21/c. The silicon complex consists of a tridentate dinegative Schiff base ligand bound to a di-phenyl-silyl unit. The coordination geometry of the penta-coordinate silicon atom is a distorted trigonal bipyramid.

Silicon corrole functionalized color catcher strips for fluoride ion detection

Monitoring fluoride ions in drinking water is essential for human health. The ability of (Hydroxy)[5,10,15-tritolylcorrolato]silicon complexes [SiTTC(OH)] to bind fluoride ions with a significant color change is exploited to develop a simple and low-cost device to detect in situ fluoride ions in aqueous media. SiTTC(OH) was deposited on Color Catcher® (CC) strips, representing the first example of this support functionalized with a neutral receptor insoluble in water. The CC-SiTTC(OH) strip preparation protocol was optimized to obtain the best performances. Binding of F−led to a drastic color change in CC-SiTTC (OH), and colorimetric measurements were performed with an inexpensive instrumental setup similar to photo-assisted technique (PT), obtaining a LOD lower than the legal limit of 1.5 mg/L (≈ 80 µM) allowed by WHO. The value of the colorimetric variation, processed in terms of Hue, is able to measure with great accuracy the F−concentration in water samples.

Synthesis and characterization of novel Schiff base-silicon (IV) phthalocyanine complex for photodynamic therapy of breast cancer cell lines

BackgroundPhotodynamic therapy is an alternative anticancer treatment approach that promises high therapeutic efficacy. In this study, it is aimed to investigate the PDT-mediated anticancer effects of newly synthesized silicon phthalocyanine (SiPc) molecules on MDA-MB-231, MCF-7 breast cancer cell lines, and non-tumorigenic MCF-10A breast cell line. MethodsNovel bromo substituted Schiff base (3a), its nitro homolog (3b), and their silicon complexes (SiPc-5a and SiPc-5b) were synthesized. Their proposed structures were confirmed by FT-IR, NMR, UV–vis and MS instrumental techniques. MDA-MB-231, MCF-7 and MCF-10A cells were illuminated at a light wavelength of 680 nm for 10 min, giving a total irradiation dose of 10 j/cm2. MTT assay was used to determine the cytotoxic effects of SiPc-5a and SiPc-5b. Apoptotic cell death was analyzed using flow cytometry. Changes in the mitochondrial membrane potential were determined by TMRE staining. Intracellular ROS generation was observed microscopically using H2DCFDA dye. Colony formation assay and in vitro scratch assay were performed to analyze the clonogenic activity and cell motility. Transwell migration and matrigel invasion analyzes were conducted to observe changes in the migration and invasion status of the cells. ResultsThe combination of SiPc-5a and SiPc-5b with PDT exhibited cytotoxic effects on cancer cells and triggered cell death. SiPc-5a/PDT and SiPc-5b/PDT decreased mitochondrial membrane potential and increased intracellular ROS production. Statistically significant changes were detected in cancer cells' colony-forming ability and motility. SiPc-5a/PDT and SiPc-5b/PDT reduced cancer cells' migration and invasion capacities. ConclusionThe present study identifies PDT-mediated antiproliferative, apoptotic, and anti-migratory characteristics of novel SiPc molecules. The outcomes of this study emphasize the anticancer properties of these molecules and suggest that they may be evaluated as drug-candidate molecules for therapeutic purposes.

A comparative study of DFT functionals and basis sets for describing the luminescent spectra of hexacoordinated silicon complexes

This article presents a comparative study of DFT functionals - B3LYP, BHandHLYP and CAM-B3LYP in combination with basis sets – 6-311++g(d,p), cc-pVDZ and cc-pVTZ to describe the luminescence spectra of optimized structures of neutral hexacoordinated silicon complexes. The calculation accuracy of an obtained theoretical data of an electronic absorption spectra of the structures was compared with the known experimental data. To perform comparative calculations with the experimental values, a neutral optimized structure of hexacoordinated Si(bzimpy)2 complex containing 2,6-bis(benzimidazol-2'-yl)pyridine ligand was considered. A comparison of the absorption spectra of the Si(bzimpy)2 structure showed that the use of the 6-311++g(d,p) basis set in combination with the B3LYP functional gives the best agreement with the experimental data. Based on the obtained results of the study, a comparison was made of the absorption spectra of other silicon compounds - Si(bzimpyMeO)2, Si(bzimpyMe2)2 and Si(bzimpyMeOMe2)2. Comparative graphs of the structures showed the proximity of the location of intense peaks for all four structures. Thus, we can say that the B3LYP functional gives the best agreement with the experimental data for neutral hexacoordinated silicon complexes. Also this shows that in a more detailed study of the absorption spectra, it can be noted that the use of the 6-311++g(d,p) basis set in combination with the B3LYP functional gives the most accurate values.

Biochemical characteristics of corn grain under the presowing seed treatment with rhizobacteria Paenibacillus polymyxa KB and chelate complex of biogenic silicon

Biochemical characteristics of corn grain under the presowing seed treatment with rhizobacteria Paenibacillus polymyxa KB and chelate complex of biogenic silicon

Silicon(IV) complexes of octaaryl-substituted porphyrazines and corrolazines: influence of macrocycle contraction on spectral-luminescence, acid-base, and redox properties.

The template cyclomerization of the iminoimide derivatives (obtained by the treatment of diarylfumarodinitriles with NH3 in methanol containing catalytic amounts of dissolved Na) in the presence of SiCl4 in pyridine leads to silicon(IV) octaarylporphyrazine complexes ((HO)2SiPzAr8, Ar = Ph, tBuPh) as a main reaction product. In the case of phenyl-substituted derivative, the formation of a distinctive Si(IV) complex as a byproduct was observed, which according to mass-spectroscopy measurement contains the macrocycle with five diphenylpyrrolic units. The treatment of bishydroxy complexes with tripropylchlorosilane in the presence of magnesium in pyridine leads to the formation of axially siloxylated porphyrazines (Pr3SiO)2SiPzAr8, followed by the reductive contraction of the macrocycle and formation of the corresponding corrolazine complexes (Pr3SiO)SiCzAr8. It is shown that the addition of acid (trifluoroacetic acid, TFA) facilitates the detachment of one siloxy group in (Pr3SiO)2SiPzAr8 and is essential for its Pz → Cz transformation. In the presence of TFA, only one meso-nitrogen is protonated in the porphyrazine complexes (Pr3SiO)2SiPzAr8 (stability constant of the protonated form pKs1 = -0.45 for Ar = Ph; pKs1 = 0.68 for Ar = tBuPh), while two consequent protonation stages are observed for the more basic corrolazine complex (Pr3SiO)SiCzPh8 (pKs1 = 0.93, pKs2 = 0.45). Both types of Si(IV) complexes are poorly fluorescent (ΦF < 0.07). The porphyrazine complexes have low ability to generate singlet oxygen (ΦΔ < 0.15), whereas the corrolazine derivative (Pr3SiO)SiCzPh8 is a very efficient photosensitizer (ΦΔ = 0.76).

Effect of rhizobacteria Paenibacillus polymyxa KB and chelate complex of biogenic silicon on photosynthetic pigments and yield of corn grain

Effect of rhizobacteria Paenibacillus polymyxa KB and chelate complex of biogenic silicon on photosynthetic pigments and yield of corn grain

Copper Complexes of Silicon Pyridine-2-olates RSi(pyO)3 (R = Me, Ph, Bn, Allyl) and Ph2Si(pyO)2

The organosilicon pyridine-2-olates 1a–1d (RSi(pyO)3, R = Me (a), Ph (b), Bn (c), Allyl (d); pyO = pyridine-2-olate) may serve as tripodal ligands toward CuCl with formation of complexes of the type RSi(μ2-pyO)3CuCl (2a–2d). In addition, for R = Allyl, formation of the more stable isomer 2d′ (κO-pyO)Si(μ2-pyO)2(μ2-Allyl)CuCl was observed. In the presence of dry air (as a source of oxygen), reactions of 1a–1d and CuCl afforded Cu(II) complexes RSi(μ2-pyO)4CuCl (3a–3d); 3a–3c in good yield, and 3d only as a side product. Reaction of Ph2Si(pyO)2 (4) and CuCl in equimolar ratio afforded, depending on reaction conditions, a series of (CuCl)n-ladder-type oligonuclear Cu(I) complexes Ph2Si(μ2-pyO)2(CuCl)n(μ2-pyO)2SiPh2 (n = 2 (52), 3 (53), 4 (54)). In all of the above compounds, the pyO group is Si–O bound and, in the case of μ2 coordination, Cu–N bound. All new compounds (1c, 1d, 2b, 2c, 2d, 2d′, 3b, 3c, 3d, 52, 53, 54) were characterized by single-crystal X-ray diffraction, and further characterization includes solution 1H, 13C, 29Si NMR spectroscopy (1c, 1d, 2b, 2c, 2d’, 53, 54), solid-state 29Si (2b, 2c, 2d′, 53, 54) and 63Cu NMR spectroscopy (2c, 2d′) as well as computational analyses of the isomerization of the couple 2d, 2d′.

Spectroelectrochemical and Theoretical Study of [Si(ttpy)2](PF6)4: A Potential Polychromatic Electrochromic Dye

Complexes consisting of earth-abundant main group metals such as silicon with polypyridine ligands are of interest for a variety of optical and electronic applications including as electrochromic colorants. Previous spectroelectrochemical studies with tris(2,2'-bipyridyl)silicon(IV) hexafluorophosphate, [Si(bpy)3](PF6)4, demonstrated an ability to control the color saturation of the potential electrochromic dye, with the intensity of the dye's green color increasing as the charge state sequentially reduces from 4+ to 1+. In this study, the synthesis of bis(4'-(4-tolyl)-2,2':6',2″-terpyridine)silicon(IV) hexafluorophosphate, [Si(ttpy)2](PF6)4, is reported along with electrochemical and spectroelectrochemical analyses. Computational modeling (density functional theory) is used to further elucidate the electrochromic properties of previously reported Si(bpy)3n+ species and the new Si(ttpy)2n+ species. While the homoleptic tris(bidentate)silicon(IV) complexes are attractive as electrochromic dyes for tunable color saturation, the bis(tridentate)silicon(IV) complexes are attractive as polychromatic electrochromic dyes.