Synthesis and structural characterization of two bond isomer copper(II) complexes via molecular modeling coupled with X-ray powder diffractometry

The reaction of the ambidentate ligand 2-(3,4-dichlorophenyl)imino-N-(2-thiazin-2-yl)thiazolidine (TdTz) with CuCl₂·2H₂O results in the formation of two new copper complexes, which has been characterized in the solid state by elemental analysis, UV-Vis-NIR diffuse reflectance, electron paramagnetic resonance (EPR) spectroscopy, magnetic measurements, infrared spectroscopy and X-ray powder diffraction. These studies have revealed that the two copper complexes are linkage isomers, which the metal atom is four-coordinated by two chloride ions and one ligand TdTz that act as a N,N bidentate ligand in one case and as a N,S bidentate ligand in the other one.     

以Schiff base为配体的Cu(Ⅱ)-金属凝胶的制备和表征

以间苯二甲醛分别与异烟肼、烟酸酰肼和2-吡啶甲酰肼反应,合成了3种含吡啶环的Schiff base配体间苯二甲醛双缩4-吡啶甲酰腙(S1)、间苯二甲醛双缩3-吡啶甲酰腙(S2)和间苯二甲醛双缩2-吡啶甲酰腙(S3);测试了这3个化合物与醋酸铜通过配位作用在不同溶剂中形成金属凝胶的能力,结果发现,配体S1与醋酸铜在DMF/H_2O和DMSO/H_2O的混合溶剂中、配体S3与醋酸铜在DMF/H_2O的混合溶剂中均可以形成金属凝胶。胶凝测试结果表明,吡啶环上N原子位置的不同,对化合物形成金属凝胶的能力有极大影响。利用扫描电子显微镜(SEM)观察了金属凝胶的微观形貌,结果表明,配体分子的结构对金属凝胶的微观形貌也有较大影响;红外光谱和紫外可见光谱的研究证明了配位作用在金属凝胶形成过程中的推动作用;X射线衍射分析(XRD)研究表明,配体S1与醋酸铜在两种混合溶剂中形成的金属凝胶均表现出了四方堆积结构。     

Gadolinium DOTA chelates featuring alkyne groups directly grafted on the tetraaza macrocyclic ring: synthesis, relaxation properties, "click" reaction, and high-relaxivity micelles

This paper reports on the synthesis and relaxivity properties of tetraacetic DOTA-type chelating agents featuring one or two alkyne groups directly grafted on the tetraaza macrocyclic ring and available for "click" reactions with azide-bearing substrates. The racemic DOTAma ligand bearing one alkyne group was obtained by a bisaminal template route. The same approach was used to prepare ligand DOTAda substituted by two alkyne groups located on two adjacent carbon atoms. The S,S enantiomer of DOTAda was also prepared by a "crab-like" condensation. This ligand is the first example of a DOTA derivative featuring two reactive functions adjacent to each other on the macrocyclic ring. A triacetic monoalkyne ligand (DO3ma) was also synthesized for comparison purposes. NMR studies indicate that the Yb(III) chelates of DOTAma and DOTAda adopt two conformations in solutions in which the tetraaza ring is rigidified. The hydration state of the Eu(III) chelates was determined by luminescence spectroscopy, and the water exchange time of the Gd(III) complexes was measured by (17)O NMR. Ring substitution accelerates the water exchange. These data were used to interpret nuclear magnetic relaxation dispersion curves of the Gd(III) chelates. Two long aliphatic chains have been added to DOTAda by a "click" procedure to form the (C18)(2)DOTAda ligand. The corresponding Gd(III) complex forms micelles of unusually high relaxivity presumably because of the close proximity of the aliphatic chains on the macrocyclic ring that ensures a rigid double anchoring into the micelles.     

Synthesis,crystal structures,and antimicrobial activity of two thiocyanato-bridged dinuclear copper(II) complexes derived from 2,4-dibromo-6-[(2-diethylaminoethylimino)methyl]phenol and 4-nitro-2-[(2-ethylaminoethylimino)methyl]phenol

A pair of structurally similar thiocyanato-bridged dinuclear Cu(II) complexes derived from the Schiff bases 2,4-dibromo-6-[(2-diethylaminoethylimino)methyl]phenol and 4-nitro-2-[(2-ethylaminoethylimino)methyl]phenol has been prepared and characterized by physico-chemical and spectroscopic methods. Each Cu atom is five-coordinate in a square-pyramidal geometry, with one O and two N atoms of one Schiff base ligand and one N atom of a bridging thiocyanate ligand defining the basal plane, and with one terminal S atom of another bridging thiocyanate ligand occupying the apical position. Antimicrobial activities of the Schiff bases and the two complexes have been tested. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Bis(tetraphenylphosphonium) (hexasulfido‐2κ2S1,S6)di‐μ‐sulfido‐disulfido‐1κ2S‐tungsten(VI)zinc(II) acetone solvate

The title complex, (C₂₄H₂₀P)₂[WZnS₄(S₆)]·C₃H₆O or (Ph₄P)₂[WS₂(μ‐S)₂{Zn(S₆)}]·Me₂CO, was unexpectedly obtained on attempted recrystallization of a mixed tungten–zinc complex of a tris(pyrazolato)borate ligand. The two metal centres of the anion have distorted tetrahedral coordination and the two tetrahedra share one S...S edge; tungsten is additionally coordinated by two terminal sulfide ligands and zinc by a chelating S₆²⁻ ligand, which has one central S—S bond significantly longer than the other four, a pattern found to be consistent for this ligand. This is the first reported example of a tetrahedral zinc centre bridging an edge of a single tetrathiotungstate(VI) or tetrathiomolybdate(VI) anion, although there are many previous examples with other metals.     

含樟脑衍生物氰基桥联双金属配合物的合成、结构及磁性质

采用樟脑衍生物为配体，分别合成了氰基桥联Cu(Ⅱ)-Fe(Ⅲ)-Cu(Ⅱ)三核配合物[{Cu(D,L-La)₂}₂Fe(CN)₆](ClO₄) (1)和Mn(Ⅲ)-Fe(Ⅲ)双核配合物[Mn(D,L-Lb)(DMF)(Tp)Fe(CN)₃]·(H₂O)₆ (2)。晶体结构分析表明，化合物1中Cu(Ⅱ)离子处于五配位的配位环境，分别和1个D-La，1个L-La及[Fe(CN)₆]^3-中的1个氰基配位，2个Cu(Ⅱ)离子通过[Fe(CN)₆]^3-桥联。通过分子间氢键作用，化合物1形成二维超分子网络结构。化合物2中，[(Tp)Fe(CN)₃]^-通过其中的1个氰基与[Mn(D，L-Lb)]⁺桥联，其中Mn(Ⅲ)离子为六配位，分别和四齿配体Lb的2个氧原子和2个氮原子、DMF的1个氧原子及[(Tp)Fe(CN)₃]^-中的氰基氮原子配位。磁性研究表明，在化合物1中，Cu(Ⅱ)离子与Fe(Ⅲ)离子之间表现出铁磁相互作用，用哈密顿函数H=-2J(S₁·S₂+S₂·S₃)对其χ_MT-T曲线进行拟合，得到1的朗日因子g为2.190，交换常数J为0.55 cm^-1。     

One- and two-electron reduced 1,2-diketone ligands in [CrIII(L*)3] (S = 0) and Na2(Et2O)2[VIV(LRed)3] (S = 1/2)

The electronic structures of chromium and vanadium centers coordinated by three reduced 1,2-diketones have been elucidated by using density functional theory (DFT) calculations and a host of physical methods: X-ray crystallography; cyclic voltammetry; ultraviolet-visible (UV-vis), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) spectroscopy; and magnetic susceptibility measurements. The metal center in octahedral [CrIII(L*)3]0 (1), a CrIII (d3) ion is coupled antiferromagnetically to three monoanionic ligand pi-radicals affording an S ) 0 ground state. In contrast, Na2(Et2O)2[VIV(LRed)3] (2) (S ) 1/2), possesses a central VIV (d1) ion O,OE-coordinated to three closed-shell, doubly reduced ligands which in turn are coordinated by two Na cations enforcing a trigonal prismatic geometry at the vanadium center. 2 can be oxidized electrochemically by one and two electrons generating a monoanion, [V(L)3]1-, and a neutral species, [V(L)3]0, respectively. DFT calculations atthe B3LYP level show that the one-electron oxidized product contains an octahedral VIV ion coupled antiferromagnetically to one monoanionic ligand pi-radical [VIV(L*)(LRed)2]1- (S ) 0). In contrast, the two-electron oxidized product contains a VIII ion coupled antiferromagnetically to three ligand pi-radicals in an octahedral field[VIII(L*)3]0 (S ) 1/2).     

Syntheses, Crystal Structures and Theoretical Calculation of Two Transition Metal Dinuclear Complexes

Two transition metal dinuclear complexes of [Mn2（OOCC6H4SSC6H4COO）- （Phen）2（H20）]n 1 and [CuE（OOCC6H4S）2（Phen）2] 2 were hydrothermally synthesized by the reaction of equivalent metal dichloride with 2,2＇-dithiobis（benzoic acid） （HE-DTBB）. Structure analysis indicates that each Mn2＋ ion in I is coordinated by one chelate phen ligand, one bridging water molecule and three DTBB ligands forming Mn2＋ dinuclear units which are further linked into one-dimensional chain by DTBB ligand. Under similar reaction conditions, the 2,2＇-dithio- his（benzoic acid） ligand undergoes thiol reduction to form 2-mercaptobenzoic （H-2-MBA） in 2 where two Cu2＋ ions are coordinated by phen and MBA ligands only constructing a dinuclear unit.     

Formation of mono(dithiolene)-thiocarboxamido complexes in reactions of thio(dithiocarbamato)-Mo/W complexes and dimethyl acetylenedicarboxylate

Reactions of TpMS(S(2)CNEt(2)) with dimethyl acetylenedicarboxylate in dichloromethane produce olive green/black TpM{S(2)C(2)(CO(2)Me)(2)}(SCNEt(2)-kappa(2)S,C) (M = Mo (1), W (2); Tp = hydrotris(3,5-dimethylpyrazol-1-yl)borate). The seven-coordinate complexes exhibit pseudo-octahedral (1) and distorted pentagonal bipyramidal (2) coordination spheres comprised of tridentate fac-Tp, bidentate dithiolene, and thiocarboxamido-kappa(2)S,C ligands. In the solid state, molecules of 1 exhibit pseudo-C(s)() symmetry, with the thiocarboxamide NEt(2) group in a cleft in the Tp ligand. Molecules of 2 have C(1) symmetry in the solid state; here, the thiocarboxamide unit is orientated along one of the W-S(dithiolene) bonds with its NEt(2) group projecting away from the Tp ligand. Both complexes possess effective C(s)() symmetry in solution. Reaction of TpMoI(CO)(3) with AgS(2)CNEt(2) affords olive green TpMo(S(2)CNEt(2))(CO)(2) (3), which reacts with propylene sulfide in a new synthesis for TpMoS(S(2)CNEt(2)), the starting material for 1. Complex 3 exhibits a distorted pentagonal bipyramidal structure, the axial sites being defined by a Tp nitrogen atom and a carbonyl ligand, the pentagonal plane by the remaining nitrogen and carbonyl donors and the two sulfur atoms of the bidentate dithiocarbamate ligand.     

Dipyrrinphenol-Mn(III) complex: synthesis, electrochemistry, spectroscopic characterisation and reactivity

Herein, we report the manganese complex with a novel trianionic ligand, the pentafluorophenyldipyrrinphenol ligand DPPH(3). The X-ray crystal structure reveals that the Mn(III) complex exists in a dimeric form in the solid state. Electrochemical studies indicate two quasi-reversible one electron oxidation processes. EPR data on the one electron oxidised species in solution support the formation of a monuclear Mn complex with an S = 3/2 spin system. Preliminary studies towards epoxidation reactions were tested in the presence of iodosylbenzene (PhIO) and are in favour of an oxygen-atom-transfer (OAT) reaction catalyzed by the Mn(III) complex.     

铂氢化物trans-[PtH(tu)(PPh_3)_2]Cl(tu)(THF)_2(tu=SC(NH_2)_2)的结构

制得含硫脲配体的铂氢化物单晶trans-[PtH(tu)(PPh_3)_2]Cl(tu)(THF)_2,其结构测定结果为:C_(46)H_(55)N_4O_2P_2S_2ClPt M=1052.6,单斜晶系,空间群为 P2_1/c,a=12.103(1),b=21.619(3),c=20.189(4)(?),β=103.31(0)°,V=5140(2)(?)~3,Z=4,D_c=1.360g·cm~(-3),F(000)=2128,R=0.050,R_w=0.063.Pt(Ⅱ)与两个磷、一个硫脲分子的硫和一个氢相配合,形成四边形配位。     

catena‐Poly[[{4‐bromo‐2‐[2‐(di­methyl­amino)­ethyl­imino­meth­yl]­phenolato}­copper(II)]‐μ‐thio­cyanato]

The title complex, [Cu(C₁₁H₁₄BrN₂O)(NCS)]_n, is an inter­esting thio­cyanate‐bridged polynuclear copper(II) compound, which crystallizes with two independent mol­ecules in the asymmetric unit. Each Cu^II atom is five‐coordinate in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base ligand and one terminal N atom of a bridging thio­cyanate ligand defining the basal plane, and one terminal S atom of another bridging thio­cyanate ligand occupying the apical position. The {4‐bromo‐2‐[2‐(dimethyl­amino)ethyl­imino­meth­yl]phenolato}copper(II) units are linked by the bridging thio­cyanate ligands, forming polymeric chains running along the a axis. There are weak inter­molecular C—H⋯O and C—H⋯S hydrogen bonds between the chains in the crystal structure.     

Synthesis,characterization, DFT calculations,and antimicrobial activity of Pd(II) and Co(III) complexes with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard’s T reagent

Complexes of Pd(II) and Co(III) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and Girard T reagent were synthesized, characterized, and their antimicrobial activities were evaluated. The ligand and the complexes were characterized by elemental analysis, IR and NMR spectroscopies, and X-ray crystallography. In both complexes, the deprotonated ligand was coordinated to the metal through the phosphorus, the imine nitrogen, and the carbonyl oxygen atoms. In the octahedral Co(III) complex, two molecules of ligands were coordinated to metal ion, while square-planar environment of Pd(II) complex was constituted of one tridentate ligand and chloride in the fourth coordination place. The ligand and complexes showed moderate antibacterial activity. The molecular structures of the obtained metal complexes and the relative stabilities of two stereoisomers of the ligand were calculated using density functional theory at the S12g/TZ2P level.     

Synthesis,Crystal Structure and Luminescent Properties of [Ag（bzdmpymt）]6·2MeOH （bzdmpymtH = 5-Benzyl-4,6-dimethylpyrimidine-2-thione）

Reaction of AgAc with bzdmpymtH in MeOH resulted in the title compound [Ag（bzdmpymt）]6-2MeOH （1.2MeOH）, which was structurally characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. 1.2MeOH belongs to the triclinic system, space group Pi, with a = 10.930（2）, b = 11.646（2）, c = 16.794（3）A, a = 103.97（3）, β = 97.07（3）, γ = 97.94（3）°, V = 2027.2（7） A3, Z = 1, μ = 1.629 mm^-1, Dc = 1.710 mg/m3, T = 193（2） K, CsoH86Ag6N12O2S6, Mr = 2087.25, F（000） = 1044, S = 1.034, R = 0.0355 and wR = 0.0709. In 1.2MeOH, six silver（I） atoms are held together by six bzdmpymt ligands through N and S atoms to form a water-wheel-shaped structure. Each Ag atom is coordinated by two S atoms from two bzdmpymt ligands and one N atom from the third bzdmpymt ligand, giving a trigonal planar coordination geometry. Interactions between the CH3 group of bzdmpymt ligand and one pyrimidyl nitrogen atom in an adjacent molecule afford a one-dimensional hydrogen-bonding chain running along the b axis. The luminescent property of 1.2MeOH was also investigated.     

Trefoil-shaped metallacycle and metallacage via heteroleptic self-assembly

Template-oriented multi-component synthesis method has been proven to be an exceedingly reasonable and excellent method for the synthesis of giant two-dimensional (2D) and three-dimensional (3D) supramolecules, but designing and constructing heteroleptic and controllable self-assembly without unexpected by-products remains a challenge. Here we report two discrete trefoil-shaped metallacycle S1 and metallacage S2 by heteroleptic self-assembly using one hexaphenylbenzene core ligand and two capping ligands. The 2D trefoil-shaped metallacycle S1 could resemble the emblem of the classic ‘Mitsubishi’ motif. The use of template-oriented ligand and bent spacer ligand promotes the quantitative formation of the desired 3D trefoil-shaped metallacage S2. The formed metallacage S2 possesses a molecular weight up to 36 kDa, diameter 6.6 nm and height 3.0 nm. All supramolecular coordination complexes were fully characterized by NMR spectroscopy (¹H NMR, 2D COSY, 2D NOESY, 2D DOSY), high-resolution electrospray ionization mass spectrometry ESI-MS, ESI-TWIM-MS, TEM and AFM.     

Synthesis, crystal structure, aqueous speciation, and kinetics of substitution reactions in a water-soluble Mo3S4 cluster bearing hydroxymethyl diphosphine ligands

The [Mo3S4Cl3(dhmpe)3]Cl ([1]Cl) cluster has been prepared from [Mo3S7Cl6]2- and the water-soluble 1,2-bis(bis(hydroxymethyl)-phosphino)ethane (dhmpe, L) ligand. The crystal structure has been determined by X-ray diffraction methods and shows the incomplete cuboidal structure typical of the M3Q4 clusters (M=Mo, W; Q=S, Se), with a capping sulfide ligand to the three metal centers and the other three sulfides acting as bridges between two Mo atoms. The octahedral coordination around each metal center is completed with a chlorine and two phosphorus atoms of one L ligand. The chemistry of aqueous solutions of [1]Cl is dominated by the formation of the [Mo3S4L(L-H)2(H2O)]2+ complex ([2]2+), where the three chlorides have been replaced by one water molecule and two alkoxo groups of two different dhmpe ligands, thus leading to a solution structure where the three metal centers are not equivalent. A detailed study based on stopped-flow, 31P{1H} NMR, and electrospray ionization mass spectrometry techniques has been carried out to understand the behavior of [2]2+ in aqueous solution. In this way, it has been established that the addition of an excess of X- (Cl-, SCN-) leads to [Mo3S4X3(dhmpe)3]+ complexes in three resolved kinetic steps that correspond to the sequential coordination of X- at the three metal centers. However, whereas the first two steps involve the opening of the chelate rings formed with the alkoxo groups of the dhmpe ligands, the third one corresponds to the substitution of the coordinated water molecule. These results demonstrate that the asymmetry introduced by the closure of chelate rings at only two of the three Mo centers makes the kinetics of the reaction deviate significantly from the statistical behavior typically associated with M3Q4 clusters. The results obtained for the reaction of [2]2+ with acid and base are also described, and they complete the picture of the aqueous speciation of this cluster.     

Access to new Janus head ligands: linking sulfur diimides and phosphanes for hemilabile tripodal scorpionates

Reactions of lithium dialkyl/phenyl phosphanylmethylides, RR'PCH(X)Li (R, R' = Me, Et, Ph and R = Me, R' = Ph; X = H or Me), with sulfur diimides S(NR')2 (R' = (t)Bu or SiMe3) in an equimolar ratio yielded Janus head complexes with the structural motif [Li{RR'PCH(X)S(NR')2}]2 (R' = (t)Bu, SiMe3). The basic core of these dimeric complexes is composed of a (LiN)(2) four-membered ring containing two four-coordinated lithium atoms. A lithium complex of the new Janus head ligand with another structural motif [TMEDA·Li{Ph(2)PCH(2)S(NSiMe3)2}] (6) could be isolated from the reaction of [Ph2PCH2Li·TMEDA] with S(NSiMe3)2. Two monomeric complexes [Mg{Me2PCH2S(NR')2}2] (7, 8) were synthesised by a straightforward reaction of [Li{Me2PCH2S(NR')2}2] with MgCl2 in pentane. The magnesium atom is chelated by one phosphorus atom and two nitrogen atoms of each unit of the hemilabile ligand in a tripodal manner, leading to octahedral geometry around the magnesium cation. A complete analysis of [Ph2PCH2(SNSiMe3)(HNSiMe3)] (9) is also described in which one nitrogen atom of the imido moiety is protonated.     

Synthesis and Crystal Structure of Binuclear Silver(Ⅰ)Complex with 2-nitro-(2-pyridylsulfanylmethyl)benzene

The reaction of 2-nitro-(2-pyridylsulfanylmethyl)benzene L with silver nitrate produces a centrosymmetric binuclear complex bis(2-nitro-(2-pyridylsulfanylmethyl)benzene-N,S)-bis(nitrato-O,O)-disilver(Ⅰ), [AgLNO3]2 1. The crystal is of triclinic, space group P1, with a = 7.383(3), b = 8.340(3), c = 12.003(4) A, a = 95.069(6), β = 93.498(5), γ = 102.734(6)°, C24H2oAg2N6-O10S2, Mr= 832.32, V= 715.6(4) A3, Z = 1, Dc = 1.931 g/cm3, F(000) = 412, μ = 1.581 mm-1, R=0.0351 and wR = 0.0749 Each silver atom is tetrahedrally coordinated by two O atoms from bidentate nitrate, one S atom from a ligand and one N atom from another ligand. Furthermore, AgAg interactions have been observed in the complex.     

High-spin metal complexes containing a ferromagnetically coupled tris(semiquinone) ligand

The tris-bidentate ligand 1,3,5-tris(5'-tert-butyl-3',4'-dihydroxyphenyl)benzene ((TBCat)(3)Ph) was synthesized. The reaction of this molecule in basic solution with two paramagnetic acceptors, i.e., a nickel(II)minus signtetraazamacrocyclic ligand complex (Ni(CTH)) (CTH = dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) and manganese(II)-hydrotris[3-(4'-cumenyl)-5-methylpyrazolyl]borate (Mn(Tp(Cum,Me))), yielded two complexes whose analytical formulas are consistent with those of trinuclear complexes. Spectroscopic and magnetic measurements suggest that these derivatives contain divalent metal ions coordinated to the tris(semiquinone) form of the ligand. Analysis of the magnetic data shows that the pi-connectivity of the ligand enforces ferromagnetic coupling between the three semiquinone units of the molecule, giving rise to complexes with S = 9/2 (M = Ni(II)) and S = 6 (M = Mn(II)) ground states. The coupling within the tris(semiquinone) unit is quite large (J = -26 cm(-1) for the nickel(II) derivative and J = -40 cm(-1) for the manganese(II) one, using the general exchange Hamiltonian H = sigma J(ij)S(i)S(j)), and it is of the same order of magnitude as that observed in an analogous series of bis(semiquinone) complexes that we recently reported.     

Unprecedented formation of novel phosphonodithioate ligands from diferrocenyldithiadiphosphetane disulfide

The reaction of the phosphetane disulfide, FcP(S)S 2P(S)Fc ( 1) (Fc = (eta (5)-C 5H 5)Fe(eta (5)-C 5H 4)), the ferrocenyl analogue of the Lawesson reagent, with gold and palladium complexes leads to the unprecedented formation of phosphonodithioate ligands upon coordination to the metal centers. The reaction of 1 with gold complexes such as [AuCl(PR 3)] affords the species [Au{S 2P(OH)Fc}(PR 3)] (PR 3 = PPh 3 ( 2), PPh 2Me ( 3)), in which the phosphonodithioate ligand Fc(OH)PS 2 (-) has been formed. The same ligand is present in the compound [Au 2{S 2P(OH)Fc} 2].[N(PPh 3) 2]Cl ( 4), obtained by reaction of 1 with [N(PPh 3) 2][AuCl 2]. It crystallizes with one molecule of [N(PPh 3) 2]Cl, whereby complex 4 acts as an anion receptor and forms strong hydrogen bonds between the chloro and the hydroxyl groups. The reaction with palladium derivatives is different; two complexes, [Pd 2(S 4OP 2Fc 2) 2] ( 5) and [Pd 4Cl 4(S 4OP 2Fc 2) 2] ( 6), are obtained in molar ratio 2:1 and 1:1, respectively. In these complexes a new phosphonodithioate ligand is present and probably arises from the condensation of two molecules of Fc(OH)PS 2 (-). Complex 5 has also been characterized by X-ray methods.