Search

The synthesis of homoleptic 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (HL) complexes of aluminium and Group 4 metals (Ti, Zr or Hf) was achieved by ligand displacement from AlEt3 and [M(PhCH2)4](M = Ti, Zr or Hf) with HL. The products were characterized by 1H and 13C NMR, which showed the sugar ligands to be equivalent and free to rotate about the M–O bond, even at 193 K. Pyridine adducts of all the complexes were obtained and the crystal structures of two of them, [AlL3(py)] and [ZrL4(Py)2], determined. The reaction of [AlL3] with two equivalents of 4,4′-bipyridine (4,4′-bipy) led to the formation of the one-to-one adduct [AlL3(4,4′-bipy)]. Complexation of [TiL4] by 1,10-phenanthroline (phen) gave the Lewis-base adduct [TiL4(phen)] which shows a strong steric effect of the base and a clear differentiation of the sugar ligands cis and anti to the N donor atoms. Optical rotatory power values [α]D were measured for all the complexes. Crystallographic details: [AlL3(py)], trigonal, space group R3, a=b=c= 10.639(2)A, α=β=γ= 93.18(2)°, Z= 1 and R= 0.049 for 2154 independent observed reflections; [ZrL4(py)2], triclinic, space group P1, a= 13.843(1), b= 12.682(1), c= 10.942(1)A, α= 87.73(1), β= 73.32(1), γ= 66.96(1)°, Z= 1 and R= 0.057 for 3336 independent observed reflections.

The reaction of [V(Mes) 3 (THF)] [Mes≡2,4,6-Me 3 C 6 H 2 ] with free α-amino acids in non-protic solvents led to the synthesis of homoleptic mononuclear hexacoordinate vanadium(III) complexes VA 3 [AH=L-proline, 1;AH=D-proline, 2;AH=L-phenylalanine, 3;AH=D-phenylalanine, 4; AH=D,L-phenylalanine, 5;AH=L-tryptophan, 6;AH=L-valine, 7]. The solubility of the products varies according to the nature of the amino acid. The crystalline solids contain solvents of crystallization.

The reaction of the tetralithium meso-octaethylporphyrinogen Et 8 N 4 Li 4 (THF) 4 with ZrCl 4 (THF) 2 led to the formation of [(η 5 -η 1 -η 5 -η 1 -Et 8 N 4 )Zr(THF)] (3), containing two η 5 and two η 1 pyrrolyl anions bonded to zirconium. Such a complex acts as a bifunctional acid-base system able to dissolve ionic salts in their monomeric or dimeric form in hydrocarbon solution. The reaction of 3 with NaH in toluene led to the complexation of NaH via the interaction of the hydride with the Lewis acid Zr and the η 5 complexation of Na by the pyrrolyl anions.

Cyclotetramerization of a mixture of 3,4-dicyano-1,2,5-thiadiazole or 3,4-dicyano-1,2,5-selenodiazole with 3,6-diamyloxyphthalo-dinitrile gives new unsymmetrical porphyrazines with annulated 1,2,5-thia(seleno)diazole and 3,6-diamyloxybenzene rings; the structures of the 1:3 products H2{XN2}{3,6-(OAm)2Bz}3Pz (X = S, Se) has been elucidated by single-crystal X-ray diffraction.

[Zr(η8-C8H8)(OAr)(Cl)](Ar = 2,6-But2-C6H3)2 was transformed into the corresponding methyl, [Zr(η8-C8H8)(Me)(OAr)]3 and dimeric hydrido, [{Zr(η8-C8H8)(OAr)}2(µ-H)2]4 derivatives; the latter complex reduced CO to formaldehyde to produce the dimeric [{Zr(η8-C8H8)(OAr)}2(µ-CH2O)]5, isostructural to 4.

Tantalum pentachloride–methylene chloride system performs C–C and C–H bond cleavages on alkylbenzenes producing the 5,7-diisopropyl-1,3,3-trimethylindan-1-yl cation from 1,3,5-triisopropylbenzene, and the 9,10-dihydro-9-anthryl cation from both 1,2,4,5-tetramethylbenzene and 1,2,3,5-tetramethylbenzene both having TaCl6– as a counteranion, and they have been characterized by X-ray analysis.

The reaction of TiCl 4 with different isocyanides did not lead to any insertion of the isocyanide functionality into the Ti-Cl bond but to simple adducts such as {[TiCl 3 (2,6-Me 2 C 6 H 3 NC)] 2 (μ 2 -Cl) 2 }, [(TiCl 4 ) 2 (μ 2 -O=P-(OEt 2 CH 2 NC) 2 ], and [(TiCl 4 ) 2 (μ 2 -O=C(OEt)CH 2 NC) 2 ]. This ruled out any organometallic pathway in the Passerini reaction assisted by TiCl 4 . The present mechanism is proposed on the basis of the isolation and structural characterization of the key intermediate [TiCl 3 (μ 3 -OC(Me,Ph)C(Cl)=NCH 2 C(OEt)=O] derived from the reaction of PhCOCH 3 and CNCH 2 COOEt assisted by TiCl 4

The deprotonation of tmtaaH 2 by LiBu n or LiMe gave a red solid, which upon recrystallization from DME was isolated as crystals suitable for X-ray analysis, [(tmtaa) 2 Li 4 (DME)3] (2). The lithium derivative was used in situ for the synthesis of [(tmtaa)Ti(Cl)] (3), [(tmtaa)Ti(Cl) 2 -C 6 H 6 (4), and [(tmtaa)M(Cl) 2 ]-2THF (M=Zr, 5; M=HC, 6). The structure of 2 shows a very pronounced bent cavity derived from the saddle-shape conformation of the ligand

The alkylation of [Ti(salen)Cl2]1[salen =N,N′-ethylenebis(salicylideneiminate)] using LiMe in toluene gave the first octahedral trans-dimethyltitanium(IV) derivative, [Ti(salen)Me2]2. Complex 2 is thermally labile and a thermally induced methyl migration to the ligand salen was observed in solution. The isolation of a compound derived from an aryl migration to the ligand was achieved in the reaction of MgBr(mes)(mes = 2,4,6-Me3C6H2) with 1 leading to [Ti(L)(mes)]3, containing the mesityl group bonded to the metal, and the second one attached to the carbon of the imino group of salen. The alkylation reaction is greatly affected by the solvent. When alkylation or arylation of 1 is carried out in tetrahydrofuran (thf) with MgXR (R = Ph or mes) reductive arylation of 1 occurs with the isolation of the corresponding titanium(III) derivatives [Ti(salen)R(thf)](R = Ph 4 or mes 5). Crystallographic details: complex 2, orthorhombic, space group P212121, a= 22.795(2), b= 14.734(1), c= 6.849(1)A, Z= 4, and R= 0.047 for 882 independent observed reflections; 3, monoclinic, space group P21/n, a= 12.804(1), b= 26.566(3), c= 10.014(1)A, β= 95.27(1)°, Z= 4, and R= 0.057 for 3625 observed reflections; 4, orthorhombic, space group P212121, a= 18.455(2), b= 14.633(2), c= 13.172(2)A, Z= 4, and R= 0.118 for 1524 observed reflections.

Reaction of VCl 3 (THF) 3 with tmtaaLi 2 gave the monochloro derivative [(tmtaa)V(Cl)] (1). It was converted by conventional methods into the corresponding alkyl and aryl derivatives [(tmtaa)V(R)] [R=Me (2), CH 2 Ph (3), Ph (4), 2,4,6-Me 3 C 6 H 2 =Mes (5)]. A nonconventional synthetic route leading to the [(tmtaa)V III ] organometallic derivatives uses [(tmtaa)V(O)] (6) starting material. The structures of 1, 4, and 5 have been determined by an X-ray analysis

The syntheses of [M(η8-C8H8)(η4-C8H8)](M = Zr, 2 or Hf, 3) and [M{η8-C8H6(SiMe3)2}{η4-C8H6(SiMe3)2}](M = Zr, 4 or Hf, 5) are reported. The η8 and η4 bonding modes for C8H8 were established in the solid state by X-ray analyses, while in solution a single C8H8 environment was observed by 1H NMR spectroscopy even at low temperature in accord with fluxional behaviour for these compounds. Complexes 2–5 behave as Lewis acids toward tetrahydrofuran, NH3 and ButNC and the adducts [Zr(η8-C8H8)(η4-C8H8)(NH3)]6 and [M(η8-C8H8)(η4-C8H8)(CNBut)](M = Zr, 7 or Hf, 8) have been isolated and characterized by X-ray analysis. Crystallographic details: 2, monoclinic, space group P21/c, a= 13.754(1), b= 7.798(1), c= 12.753(1)A, β= 114.02(1)°, Z= 4 and R= 0.037 for 1267 independent observed reflections; 5, orthorhombic, space group Pca21, a= 14.418(1), b= 11.285(1), c= 18.898(1)A, Z= 4 and R= 0.036 for 2239 independent observed reflections; 6, orthorhombic, space group P212121, a= 9.815(1), b= 14.129(2), c= 9.561(1)A, Z= 4 and R= 0.022 for 1556 independent observed reflections; 7, triclinic, space group P, a= 11.172(1), b= 13.469(1), c= 14.303(1)A, α= 62.80(1), β= 78.01(1), γ= 77.26(1)°, Z= 4 and R= 0.028 for 2994 independent observed reflections.

Reference EPFL-ARTICLE-203046doi:10.1021/ic00345a016View record in Web of Science Record created on 2014-11-07, modified on 2017-11-27

The reaction of MCl4·2thf (thf = tetrahydrofuran) with the sodium salt of quadridentate Schiff bases [L =N,N′-ethylenebis(acetylacetoneiminate)(acen), N,N′-ethylenebis(salicylideneiminate)(salen), N,N′-ethylenebis(α-methylsalicylideneiminate)(dmsalen), or N,N′-o-phenylenebis(salicylideneiminate)(salphen)] yields the complexes [MLCl2(thf)]. X-Ray analyses showed for all of them that the metal ion is seven-co-ordinate with a pseudo-pentagonal bipyramidal geometry. Details of the structures of [Zr(acen)Cl2(thf)](5), [Zr(salphen)Cl2(thf)]·0.5thf (10), and of the corresponding isostructural hafnium complex [Hf(salphen) Cl2(thf)]·0.5thf (11) are reported. The equatorial plane of the bipyramid is defined by the N2O2 donor atoms and by the oxygen atom from thf, while the two chlorine atoms are trans to each other [Cl–Zr–Cl 169.1 (1), (5); 165.2(1), (10); Cl–Hf–Cl 166.3(1)°, (11)]. Recrystallization of the seven-co-ordinate complexes from toluene removed the thf leading to six-co-ordinate complexes. The structural determination of the isostructural [Zr(acen)Cl2](12) and [Hf(acen)Cl2](13) showed the six-co-ordination of the metal with the two chlorines assuming a cis arrangement [Cl–Zr–Cl 87.2(1), (12); Cl–Hf–Cl 87.4(1)°, (13)]. Bond lengths within the co-ordination sphere are significantly shorter in the six-co-ordinate complexes. The cis and trans isomers do not interconvert in solutions of non-co-ordinating solvents, i.e. C6H6 or CH2Cl2, as shown by their distinctive 1H n.m.r. spectra. In the absence of geometrical constraints zirconium(IV) prefers six-co-ordination and a cis arrangement of the chloride ligands. This was confirmed by synthesizing [Zr(msal)2Cl2](15)(msal =N-methylsalicylideneiminate), [Cl–Zr–Cl 97.9(1)°] containing a bidentate Schiff-base ligand. Its crystallization from thf gave the unsolvated six-co-ordinated form. Crystallographic details: complex (5), space group P, a= 8.401 (1), b= 15.987 (2), c= 7.805(1)A, α= 98.41 (1), β= 90.32(1), γ= 76.65(1)°, Z= 2, and R 0.042 for 3 713 observed reflections; (10), space group P, a= 12.759(2), b= 13.332(2), c= 7.587(1)A, α= 91.60(2), β= 98.45(1), γ= 85.30(1)°, Z= 2, and R 0.033 for 3 813 observed reflections; (11), space group P, a= 12.737(7), b= 13.269(7), c= 7.564(4)A, α= 91.48(1), β= 98.56(1), γ= 85.26(1)°Z= 2, and R 0.027 for 4 227 observed reflections; (12), space group P21/n, a= 24.150(5), b= 9.160(2), c= 7.282(1)A, β= 90.90(1)°, Z= 4, and R 0.034 for 1 894 observed reflections; (13), space group P21/n, a= 24.096(10), b= 9.161 (4), c= 7.262(3)A, β= 90.87(1)°, Z= 4, and R 0.024 for 2 124 observed reflections; (15), space group P, a= 13.024(3), b= 14.522(3), c= 9.797(2)A, α= 90.10(1), β= 93.14(1), γ= 96.09(1)°, Z= 4, and R 0.044 for 3 294 observed reflections.

Complexation of metal halides M′Cln by square-planar Schiff-base complexes, i.e. ML [M = Fe, Co, Ni, or Cu; L = acen =N,N′-ethylenebis(acetylacetoneiminate), salen =N,N′-ethylenebis(salicylideneiminate), or salphen =N,N′-o-phenylenebis(salicylideneiminate)] led to adducts which are intermediates in the exchange of the quadridentate ligand between M and M′. Exchange occurs if M′ is in an higher oxidation state than M. Concomitant redox and ionization reactions are observed. Reaction of [Fe(acen)], (1) with MCl2·nthf (M = Fe or Zn) led to the bimetallic adducts [(thf)Fe(acen)MCl2[M = Fe, (2); Zn, (3)] containing a square-pyramidal iron, while M has a tetrahedral co-ordination geometry. A complex analogous to (2), [ClFe(salphen)FeCl(thf)2](4)(thf = tetrahydrofuran), was obtained by treating FeCl2·1.5 thf with H2 salphen in a 2:1 molar ratio in the presence of Na(OMe). This reaction gave some insight into the ligand-exchange pathway. The reaction of [M(acen)](M = Fe, Co, or Ni) complexes with TiCl4·2thf in thf led to migration of the acen ligand to titanium and formation of [Ti(acen)Cl2], (7) and the corresponding metal halide MCl2·nthf. Related results have been obtained in the reaction of [M(acen)] and TiCl3·3thf. When M = Ni or Cu complex (7) was obtained by exchange of the acen ligand and oxidation of titanium(III) by the corresponding metal halides. In the absence of a redox reaction, complexes of titanium (III) have been obtained: [Ti(acen)(thf)2][CoCl3(thf)], (10), and [Ti(acen)(thf)2]2[Fe3Cl8(thf)2], (11), respectively. The structures of complexes (2)–(4), (10), and (11) have been determined by X-ray analysis: (2) space group P, a= 14.029(2), b= 9.854(1), c= 8.092(1)A; α= 98.48(1), β= 90.96(1), γ= 107.44(1)°, Z= 2, and R= 0.065 for 1 360 observed reflections; (3), space group P, a= 14.006(3), b= 9.823(2), c= 8.077(2)A, α= 98.49(1), β= 90.90(1), γ= 107.57(1)°Z= 2, and R= 0.072 for 2 347 observed reflections; (4), space group P21/c, a= 12.882(2), b= 11.940(2), c= 21.701 (3)A, β= 95.40(1)°, Z= 4, R= 0.054 for 1991 observed reflections; (10), space group P, α= 12.735(3), b= 15.105(3), c= 8.935(2)A, α= 95.30(2), β= 94.26(2), γ= 67.91 (2)°, Z= 2, and R= 0.055 for 2 576 observed reflections; (11), space group P, α= 14.109(3), b= 14.713(3), c= 9.203(2)A, α= 99.98(2), β= 104.76(2), γ= 63.08(2)°Z= 1 for C48H84Cl8Fe3N4O10Ti2 formula unit, and R= 0.050 for 2 685 observed reflections.

The reaction of [Zr(η8-C8H8)Cl2(thf)], (1), with Mg(mes)Br (thf = tetrahydrofuran, mes = 2,4,6-Me3C6H2) in Et2O afforded the very thermally labile complex [Zr(η8-C8H8)(mes)2], (2). An X-ray analysis on complex (2) at 173 K gave insights on the possible stabilization of the hitherto unstable alkyl derivatives of (1), showing that the o-methyl groups protect the metal centre. The significant lability of the aryl ligand in complex (2) is shown by the facile double migration of the mes residue to CO forming [{Zr(η8-C8H8)[η-OC(mes)2]}2], (3). The carbonylation reaction has to be carried out at 0 °C, since complex (2) undergoes thermal decomposition at room temperature, the nature of which depends on the solvent used. In Et2O complex (2) loses mesitylene at room temperature forming [{Zr(η8-C8H8)(µ-2,4-Me2-6-CH2C6H2)}2], (7). Complex (7) has a triple-decker type structure in which two allyl units, coplanar with the η8-C8H8 rings, bridge the two zirconium atoms. Because of the allyl structure the aromaticity of the phenyl ring is lost. More drastic thermal conditions cause a hydrogen migration in (7) which rearranges to [{Zr(η8-C8H8)}2(µ-mes)(µ-2,4-Me2-6-CHC6H2)], (8), which contains an alkylidene ligand bridging two zirconium atoms. Complexes (2), (3), (7), and (8) were characterized by single-crystal X-ray analysis: (2), tetragonal, space group I41/a, a=b= 26.495(4), c= 13.711 (2)A, Z= 16, R= 0.054 for 2 468 independent observed reflections; (3), monoclinic, space group C2/c, a= 25.856(9), b= 12.444(3), c= 15.571 (8)A, β= 92.59(3)°, Z= 4, R= 0.112 for 1 659 independent observed reflections; (7), orthorhombic, space group Pbca, a= 7.831 (1), b= 19.368(2), c= 18.177(2)A, Z= 4, R= 0.045 for 949 independent observed reflections; (8), triclinic, space group P, a= 16.469(3), b= 17.452(3), c= 10.373(2)A, α= 92.35(1), β= 103.83(2), γ= 103.06(2)°, Z= 2, R= 0.041 for 3 792 independent observed reflections.

The reaction of [{LaCl3(thf)}n](thf = tetrahydrofuran) under anhydrous conditions with the sodium salt of a bi- or tri-dentate Schiff base derived from salicylaldehyde and 2,4,6-trimethylaniline [HL =N-(2,4,6-trimethylphenyl)salicylideneimine] or N,N-dimethylethylenediamine [HL′=N-(2-dimethylaminoethyl)salicylideneimine] led to the isolation of the corresponding monochloro derivatives, [La2L4(thf)2(µ-Cl)2] and [La(L′)2(HL′)Cl]. Their structures have been elucidated by X-ray crystallography.

{5,5′;19,19′-Bi[phthalocyaninato(2–)]}titanium(IV)–1-chloronaphthalene(1/1 ), [TiL]·C10H7Cl, is obtained by the reaction of [Ti(pc)Cl2](pc = phthalocyaninato dianion, [C32H16N8]2–) with Na2(pc) in 1-chloronaphthalene at 190 °C, An X-ray single-crystal structure (monoclinic, space group C/2c, a= 16.327(3), b= 18.568(4), c= 19.022(4)A; β= 94.50(1)°, Z= 4) indicates for this complex a sandwich-type structure with the titanium atom in the centre of the molecule and the two phthalocyaninato units ‘stapled’ by two inter-ring C–C σ bonds [C(11)–C(11′) 1.556(6) and C(31)–C(31′) 1.575(6)A]. Due to the staggered orientations of the two macrocyclic rings (relative rotation 45°) the planes of the two inner N4 systems (each of which is slightly distorted from planarity) form a square-antiprism, with an average interplane distance of 2.32 A(much shorter than that found in similar ‘unstapled’ complexes), and Ti–N bond distances in the range 2.17–2.26 A. The complex shows high thermal stability and can be oxidized by nitric acid to give the species [TiL]NO3. The complexes [TiL] and [TiL]NO3 show differing solid-state electrical conductivity properties.

A reactive coordinatively unsaturated iron(II) bonded to a quasi-planar O4 environment in [calix[4](OMe)2(O)2Fe] (2) has been obtained from the reaction of the free ligand 1 with Fe2Mes4 (Mes = 1,3...

The (meso-octaethylporphyrinogenato)zirconium(IV) species [(Et8N4)Zr(thf)] (1) binds the acetophenone potassium enolate [PhCOCH2K] (2) in its ion-pair form, [(η5:η1:η1:η1-Et8N4)Zr{PhC(CH2)O}K(thf)3] (3), and thus drives the aldol condensation reaction with acetophenone. The resulting aldolate, which occurs in a metallacyclic form due to the solvation of potassium by a phenyl ring, remains η1 (O)-bonded to zirconium, [(η5:η1:η1:η1-Et8N4)Zr{PhC(CH2)OC(O)C(Me)Ph}K]n (4).

μ2-[ROC(O)C(R)]-μ2-(CO)Co2(CO)5 (R = Me, iPr, tBu, Ph) bridging carbene-type dinuclear cobalt carbonyls (1) undergo a facile surface-mediated clusterification while chromatographed on silica gel, yielding [μ3-RC(O)OC]Co3(CO)9 (2a) complexes. These latter are then transformed to the corresponding (μ3-RC)Co3(CO)9 (2b) derivatives by silica-mediated decarboxylation. The X-ray diffraction structure of 2a (R = tBu) was determined and that of 2b (R = Ph) was confirmed.

The reaction of a TiMe species with carbon monoxide occurred with the complete cleavage of the CO bond and formation of the TiO unit, while the [MeC] fragment homologated a pyrrole to a 4-methylpyridine ring within the meso-octaethyl tris(pyrrole)−mono(pyridine) macrocycle.

[(Calix[4]OMe)TaCl2] (2), formed from [calix[4](OMe)2] (1) and TaCl5 via a demethylation reaction, undergoes exhaustive alkylation to [(calix[4]OMe)TaR2] (3−5), which give photochemically or thermally induced concerted dealkylation at the metal and at the methoxy group, to give [calix[4]TaR] (6−8). Double migration of alkyl groups has been observed in the reaction of 3−5 with CO and ButNC to form the corresponding η2-ketones [(calix[4]OMe)Ta(η2-COR2)] (9−11) and η2-imines [(calix[4]OMe)Ta{η2-N(But)CR2}] (12−14).

The doubly homologated meso-octaethylporphyrinogen 1, containing two pyridine and two pyrrole rings in cis arrangements, allowed the synthesis of highly reactive vanadium(III) organometallics, via the intermediacy of 2, [Et8(m-MeC5H2N)(C5H3N)(C4H2N)2Li2(THF)2], and 3, [Et8(m-MeC5H2N)(C5H3N)(C4H2N)2V−Cl]. This latter complex has been converted to the corresponding [V−Me] derivative 4, [Et8(m-MeC5H2N)(C5H3N)(C4H2N)2V−Me], which undergoes a facile carbonylation to 5, Et6(m-MeC5H2N)(C5H3N)(C4H2N)2V−OC(CEt2)(Me)]. The intermediate η2-acyl derivative thus found displayed an unusual carbenoid reactivity inserting into a C−C bond.

Recrystallization of the previously reported monosolvated bis(phthalocyaninato)niobium(IV), [Pc2Nb].CINP (CINP = 1-chloronaphthalene), has allowed isolation of a single crystal of a new solvated form, i.e. [Pc2Nb]. 3.5CINP, whose structure has been elucidated by X-ray work: space group P2(1)/n (No. 14); a = 16.765(3), b = 23.800(4), c = 19.421(4) A; alpha = gamma = 90 degrees, beta = 92.51(2) degrees; Z = 4. The sandwiched material is a "stapled" molecule, characterized by the presence of two intramolecular interligand C-C sigma bonds and highly strained phthalocyanine units, as formerly observed by crystallographic work for its Ti(IV) analogue, [Pc2Ti], and the +1 corresponding fragment, [Pc2Nb]+, present in the species [Pc2Nb](l3)(l2)0.5.3.5CINP. [Pc2Nb] appears to be reluctant to undergo further oxidation above the +1 oxidation state. Detailed theoretical studies by DFT and TDDFT methods have been developed on [Pc2Nb] and [Pc2Nb]+, also extended for comparison to the Ti(IV) complex [Pc2Ti], and an adequate picture of the ground-state electronic structure of these species has been achieved. Moreover, the excitation energies and oscillator strengths calculated for the closed-shell systems, [Pc2Ti] and [Pc2Nb]+, provide a satisfactory interpretation of their characteristic visible optical spectra and help to rationalize the similar features observed in the visible spectrum of the open-shell "stapled" complex, [Pc2Nb]. Thin solid films (100-250 nm) of [Pc2Nb] deposited on ITO (indium-doped tin oxide) show a reversible redox process in neutral or acidic aqueous electrolytes. The electrochemical and electrochromic properties of the sandwiched complex, combined with impedance and UV/visible spectral measurements, are presented and discussed. The achieved electrochemical information, while substantially in keeping with the observed chemical redox behavior and theoretical predictions, qualifies [Pc2Nb] as an "optically passive" electrode and a promising material for its use in electrochromic devices.