Synthesis,spectroscopic studies and structures of square-planar nickel(II) and copper(II) complexes derived from 2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol

Two new nickel(II) [Ni(L)₂] and copper(II) [Cu(L)₂] complexes have been synthesized with bidentate NO donor Schiff base ligand (2-{(Z)-[furan-2-ylmethyl]imino]methyl}-6-methoxyphenol) (HL) and both complexes Ni(L)₂ and Cu(L)₂ have been characterized by elemental analyses, IR, UV–vis, ¹H, ¹³C NMR, mass spectroscopy and room temperature magnetic susceptibility measurement. The tautomeric equilibria (phenol-imine, O–H?N and keto-amine, O?H–N forms) have been systemetically studied by using UV–vis absorption spectra for the ligand HL. The UV–vis spectra of this ligand HL were recorded and commented in polar, non-polar, acidic and basic media. The crystal structures of these complexes have also been determined by using X-ray crystallographic techniques. The complexes Ni(L)₂ and Cu(L)₂ crystallize in the monoclinic space group P2₁/n and P2₁/c with unit cell parameters: a = 10.4552(3) Å and 12.1667(4) Å, b = 8.0121(3) Å and 10.4792(3) Å, c = 13.9625(4) Å and 129.6616(3)Å, V = 1155.22(6) Å³ and 1155.22(6) Å³, D_x = 1.493 and 1.476 g cm^?3 and Z = 2 and 2, respectively. The crystal structures were solved by direct methods and refined by full-matrix least squares to a find R = 0.0377 and 0.0336 of for 2340 and 2402 observed reflections, respectively.     

Crystal structures,luminescence, and thermal properties of lanthanide complexes with 2,3,4-trimethoxybenzoic acid and 1,10-phenanthroline

The complexes of [Ln(2,3,4-tmoba)₃phen]₂ (Ln = Dy (1), Eu (2), Tb (3); 2,3,4-tmoba = 2,3,4-trimethoxybenzoate; phen = 1,10-phenanthroline) were synthesized and characterized by a series of techniques including the elemental analysis, IR and fluorescent spectra and TG/DSC-FTIR technology. The crystal structures were determined by X-ray crystallography. Each complex include two Ln³⁺ ions, six 2,3,4-tmoBA and two phen molecules forming a binuclear structure, giving the coordination number of nine. The three-dimensional IR accumulation spectra of gaseous products for the complexes 1 to 3 are analyzed and the thermal decomposition processes are further authenticated. Through means of differential scanning calorimeter (DSC), two solid-solid phase transition endothermic peaks were found in the complex 2, which was different from the complexes 1 and 3. The heat capacities of these complexes were measured and fitted to a polynomial equation with the least squares method for each complex on the basis of the reduce temperature x (x = [T − (T_max + T_min)/2]/[(T_max − T_min)/2]) over the range from (256.15 to 476.15) K. Subsequently, the smoothed molar heat capacities and thermodynamic functions (H_T−H_298.15 K), (S_T−S_298.15 K), and (G_T−G_298.15 K) of the complexes 1 to 3 were calculated based on the fitted polynomial of the heat capacities. The fluorescent intensity of the complexes 2 and 3 are markedly improved as well.     

Functionalized N-heterocyclic carbene iridium complexes: Synthesis,structure and addition polymerization of norbornene

Picolyl, pyridine, and methyl functionalized N-heterocyclic carbene iridium complexes [Cp¹Ir(C^N)Cl]Cl (4, C^N = 3-Methyl-1-picolyimidazol-2-ylidene), [Cp¹Ir(C^N)Cl][Cp¹IrCl₃] (5), [Cp¹Ir(C-N)Cl]Cl (6, C-N = 3-Methyl-1-pyridylimidazol-2-ylidene) and [Cp¹Ir(L)Cl₂] (7, L = 1,3-dimethylimidazol-2-ylidene) have been synthesized by transmetallation from Ag(I) carbene species, and characterized by ¹H NMR, ¹³C NMR spectra and elemental analyses. The molecular structures of 5–7 have been confirmed by X-ray single-crystal analyses. The iridium carbene complexes 4 and 6 show moderate catalytic activities (3.03 × 10⁵ g PNB (mol Ir)^?1 h^?1 and 1.70 × 10⁶ g PNB (mol Ir)^?1 h^?1) for the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as co-catalyst. The produced polynorbornene have been characterized by IR, ¹H NMR and ¹³C NMR spectra, showing it follows the vinyl-addition-type of polymerization.     

Synthesis and structure of a new scorpionate-dithio carboxyl oxovanadium complex and an organic dithio carboxyl compound

A new complex of oxovanadium(IV), V₂O₂[(HB(pz)₃)₂(pyrro)₂ (1) and a dimer-dithio carboxyl compound (C₅H₈NS₂)₂ (2) have been synthesized by the reaction of VOSO₄·nH₂O with NaHB(pz)₃ and pyrrolidine dithio carboxylic acid ammonium salt. They were characterized by element analysis, IR spectra, UV–vis spectra and X-ray diffraction. Structural analyses of 1 and 2 gave the following parameters: 1, triclinic, P-1, a = 7.732(4) Å, b = 14.285(8) Å, c = 17.802(9) Å, α = 101.314(8)°, β = 92.682(9)°, γ = 92.228(9)°, V = 1923.6(18) Å³, and Z = 4; 2, monoclinic, C2/c, a = 13.857(2) Å, b = 10.4213(18) Å, c = 9.436(2) Å, β = 97.099(2), V = 1352.1(4) Å³, and Z = 4. In complex 1, vanadium atom adopts a distorted tetragonal bipyramid structure, which is typical for oxovanadium(IV) complexes. Compound 2 is a dimer-dithio carboxyl compound with S–S bond. In addition, thermal analysis was performed for analyzing the stabilization of the complexes.     

Mixed-ligand complexes of copper(I) with diimines and phosphines: Effective catalysts for the coupling of phenylacetylene with halobenzene

New copper(I) mixed-ligand complexes 1–4 of the formula Cu(N–N)PR₃X, where N–N = 1,10-phenanthroline (phen), 2,2′-bipyridine (bpy), 5,5′-dimethyl-2,2′-bipyridine (5,5′dimbpy) and PR₃ = tricyclohexylphosphine, tris(2-cyanoethyl)phosphine and isopropyldiphenylphosphine, have been synthesized. The complexes were characterized by EA, IR, NMR and single crystal X-ray diffraction. The solution fluorescence emission spectra were measured. The single crystal X-ray analysis showed that the copper(I) ion is four-coordinate with a distorted tetrahedral geometry. The complexes catalyze the formation of diphenylacetylene from the coupling of halobenzene with phenylacetylene. The complex Cu(5,5′-dimethylbpy)P{(cyhexyl)₃}I showed the highest catalytic activity. At room temperature all four complexes exhibit, in dichloromethane, emission maxima in the 329–344 nm range, corresponding to intra-ligand excited states.     

The experimental and DFT studies of 1,3-dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide

1,3-Dimethyl-2-[4-chloro-styryl]-benzimidazolium iodide (1) was synthesized and characterized by X-ray diffraction, ¹H NMR, MS, IR, UV–vis spectra and elemental analysis. The crystals are monoclinic, space group P2₁/c, with a = 12.507(3) Å, b = 7.3259(19) Å, c = 36.705(9) Å, V = 3358.9(15) Å³, and Z = 4 (at 296(2) K). Crystal stacking scheme indicates the face-to-face π?π aromatic stacking interactions. Molecular geometries, frequencies, IR, ¹H NMR and UV–vis were calculated at DFT/TD-DFT level using two hybrid exchange–correlation functionals, B3LYP and PBE1PBE. The stability of the molecule arising from hyperconjugative interaction and charge delocalization had been analyzed using natural bond orbital (NBO) analysis. These calculations on (1) provide deep insight into its electronic structure and properties.     

Synthesis and reactions of heterodinuclear organopalladium–cobalt complexes acting as copolymerization catalyst for aziridine and carbon monoxide

A series of heterodinuclear acylpalladium–cobalt complexes having a bidentate nitrogen ligand, L₂(RCO)Pd–Co(CO)₄ (L₂ = bpy, R = Me (5), Ph (6); L₂ = tmeda, R = Me (7), Ph (8); L₂ = phen, R = Me (9), Ph (10)) are prepared by metathetical reactions of PdRIL₂ with Na⁺[Co(CO)₄]⁻ followed by treatment with CO. These complexes are characterized by NMR and IR spectroscopies and elemental analyses, and the molecular structures of 6, 8, and 9 are determined by X-ray structure analysis. Geometry at Pd is essentially square planar and the Co atom is considered to have d¹⁰ tetrahedral structure, where cobalt(-I) anion coordinates to palladium(II) cation. Heterodinuclear organopalladium–cobalt complexes are shown to catalyze copolymerization of aziridines and CO under mild conditions. Reaction of (dppe)MePd–Co(CO)₄ (1) with aziridine gives a cationic (aziridine)palladium(II) complex with [Co(CO)₄]⁻ anion, [PdMe(aziridine)(dppe)]⁺[Co(CO)₄]⁻ (13).     

Synthesis and characterization of organophosphine/phosphite stabilized N-silver(I) succinimide: crystal structure of [(Ph3P)3 · AgNC4H4O2]

Six organophosphine/phosphite stabilized N-silver(I) succinimide complexes of the type L_n · AgNC₄H₄O₂ (L = PPh₃; n = 1, 2a; n = 2, 2b; n = 3, 2c; L = P(OEt)₃; n = 1, 2d; n = 2, 2e; n = 3, 2f) have been prepared by reacting [AgNC₄H₄O₂], which can be synthesized from succinimide and excessive Ag₂O in boiling water, with triphenylphosphine or triethylphosphite in dichloromethane under a nitrogen atmosphere. These complexes were obtained in high yields and characterized by elemental analysis, ¹H, ¹³C{H} NMR, IR spectroscopy and thermal analysis (TG and DSC). The molecular structure of 2c has been determined by X-ray single crystal analysis, in which the silver atom is in a distorted tetrahedral geometry.     

Substitution reactions of thorium(IV) acetate to synthesize nano-sized carboxylate complexes

Some mixed-ligand thorium(IV) complexes with the general formula [Th(OOCCH₃)_4?nL_n] (L = anions of myristic, palmitic or stearic acid and n = 1–4) have been synthesized by the stepwise substitution of acetate ions of thorium(IV) acetate with straight chain carboxylic acids in toluene under reflux. The complexes were characterized by elemental analyses, spectral (electronic, infrared, NMR and powder XRD) studies, electrical conductance and magnetic susceptibility measurements. Doubly and triply bridged coordination modes of the ligands were established by their infrared spectra and nano-size of the complexes by powder XRD. Room temperature magnetic susceptibility measurements revealed diamagnetic nature of the complexes. Electronic absorption spectra of the complexes showed π → π*, n → π* and charge transfer transitions. Molar conductance values indicated the complex to be non-electrolytes. These are a new type of mixed-ligand thorium(IV) complexes for which a nano-sized, oxygen bridged polymeric structure has been established on the basis of physico-chemical studies.     

Electronic and vibrational circular dichroism spectroscopic study of non-covalent interactions of meso-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin with (dG-dC)10 and (dA-dT)10

The non-covalent interactions of (dG-dC)₁₀ and (dA-dT)₁₀ with 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) were studied using the combination of electronic circular dichroism (ECD), vibrational circular dichroism (VCD) spectroscopy, and UV–vis and IR absorption spectroscopy at different ratios of both components r = [oligonucleotide]/[TMPyP] = 2/1–10/1 where [oligonucleotide] and [TMPyP] are the amount concentrations of oligonucleotide per base-pair and TMPyP, respectively. It was shown that TMPyP with (dG-dC)₁₀ provided hemiintercalative binding mode for r = 4/1 that is manifested in vibrational spectra: The absorption band assigned to the C6O6 stretching vibration of guanine is shifted from 1683 to 1672 cm⁻¹, the corresponding VCD couplet from 1694(−)/1674(+) to 1684(−)/1663(+) cm⁻¹ and its intensity decreases. The absorption band assigned to the C2O2 stretching vibration of cytosine is shifted from 1652 to 1644 cm⁻¹ and its intensity increases. TMPyP with (dA-dT)₁₀ provided three binding modes: (i) external binding to the phosphate backbone, (ii) external minor groove binding for the ratios >6/1 and (iii) external major groove binging associated with the partial B- to Z-transition for the ratios <4/1. The major groove binding is manifested in VCD spectra by the intensity decrease of the bands 1655 and 1638 cm⁻¹ assigned to the thymine vibrations while the bands assigned to the adenine vibrations are unchanged. In the (dA-dT)₁₀–TMPyP complexes, the external binding to the phosphate backbone accompanied by self-stacking of porphyrins along the phosphate backbone chain is preferred at temperatures higher than 40 °C.     

Catalytic enantioselective oxidation of aromatic hydrocarbons with D4-symmetric chiral ruthenium porphyrin catalysts

The [Ru^II(D₄-Por¹)(CO)(MeOH)] (D₄-H₂Por¹ = tetrakis[(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,4:5,8-dimethanoanthracen-9-yl]porphyrin) complex 1 is an effective catalyst for asymmetric hydroxylation of aromatic hydrocarbons with 2,6-dichloropyridine N-oxide (Cl₂pyNO) as terminal oxidant. Up to 76% ee was achieved for the catalytic hydroxylation of 4-ethyltoluene, 1,1-diethylindan and benzylcyclopropane. Both electron-donating and -withdrawing substituents were found to accelerate the catalytic oxidation reaction, and a large primary H/D kinetic isotope effect (k_H/k_D = 11 at 298 K) was observed for the catalytic ethylbenzene-d₁₀ oxidation. A mechanism involving rate-limiting hydrogen atom abstraction by reactive oxoruthenium species is postulated.     

Syntheses,structures and single-molecule magnetic behaviors of two dicubane Mn4 complexes

The reaction of MnX₂ · 4H₂O (X = Cl or Br) with 2,6-bis(hydroxymethyl)-4-methylphenol (H₃L) and NaOH in methanol solution yielded two tetranuclear manganese complexes, [Mn₄(HL)₄(MeOH)₄Cl₂] (1) and [Mn₄(HL)₄(MeOH)₄Br₂] (2). Both compounds crystallize in the monoclinic space group C₂/c with cell parameters: a = 26.0945(19) Å, b = 11.4999(8) Å, c = 21.2188(16) Å, β = 121.050(1)° and z = 4 for 1 · 2Et₂O; a = 25.8145(3) Å, b = 11.6734(2) Å, c = 21.3956(3) Å, β = 120.1277(6)° and z = 4 for 2 · 2Et₂O. Both complexes consist of a mixed-valence dicubane structure, which comprises two Mn^II and two Mn^III ions. Magnetic susceptibilities and magnetization of complexes 1 and 2 in the solid state indicate that two clusters have an S = 9 ground state. Frequency-dependent out-of-phase signals of alternating current magnetic susceptibilities were observed in the low temperature range (<3 K) for both complexes indicating a slow magnetic relaxation.     

Electronic absorption study on acid–base equilibria for some pyrimidine derivatives containing semi- and thiosemicarbazone moiety

The UV–vis spectra of recently synthesized 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-one, (I), and 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-thione, (II) were studied in aqueous methanol (5%, v/v methanol). The nature of the electronic transitions and the roles of carbonyl oxygen of I and thiocarbonyl sulfur of II on the behavior of UV–vis spectra were discussed.Acid–base equilibria of the compounds against varying pH and pK_a values related equilibria were determined at an ionic strength of 0.10 M by using the Henderson–Haselbalch equation. The mean acidity constants for the protonated forms of the compounds were determined as pK_a1 = 5.121, pK_a2 = 7.929 and pK_a3 = 11.130 for I and pK_a1 = 4.684, pK_a2 = 7.245 and pK_a3 = 10.630 for II. The preferred dissociation mechanisms were discussed based on UV–vis data and a mechanism was proposed for each compound.     

Design,synthesis and physical properties of the metal complexes using π-radical with photo-excited high-spin state as a ligand

Two π-radicals, 3-pyridinyl-phenylanthracene(iminonitroxide) (3) and 3-pyridinyl-phenylanthracene-(nitronylnitroxide) (4) were designed as candidates of the ligand for the metal complexes to clarify the exchange interactions between the paramagnetic centers of the metal ions and the photo-excited high-spin states of the purely organic π-radical. Compounds 3 and 4 were synthesized and their magnetic properties were examined, showing weak antiferromagnetic interactions, θ = −1.5 K for 3 and −0.7 K for 4. The photo-excited states of 3 and 4 were investigated by time-resolved ESR and clarified that both π-radicals have the quartet (S = 3/2) high-spin states as their lowest photo-excited states. Two metal complexes [Fe(III)(L)(4)] · (BPh₄) (Low spin) (LH₂ = N,N′-bis(1-hydroxy-2-benzyliden)-1,7-diamino-4-azaheptane) and [Cu(II)(hfac)₂(4)₂] using 4 were prepared. Their magnetic behaviors are well analyzed with the Bleaney–Bowers model with J/k_B = − 0.86 K and three S = 1/2 spin cluster model with J/k_B = −1.0 K, respectively, showing weak antiferromagnetic interactions between the paramagnetic centers of the metal ions and the π-radical in the ground state.     

Dialkyl- and diaryl-platinum(II) complexes with secondary phosphines: Preparation,structure and thermal reaction giving the metallopolymer

Alkyl and arylplatinum complexes with 1,5-cyclooctadiene ligand, [PtR₂(cod)] (R = Me, Ph, C₆H₄-p-CF₃, C₆F₅), react with secondary phosphines, PHR′₂ (R′ = i-Bu, t-Bu, Ph), to afford the mononuclear platinum complexes, cis-[PtR₂(PHR′₂)₂] (1a: R = Me, R′ = i-Bu; 1b: R = Me, R′ = t-Bu; 1c: R = Me, R′ = Ph; 2a: R = Ph, R′ = i-Bu; 2b: R = Ph, R′ = t-Bu; 2c: R = R′ = Ph; 3a: R = C₆H₄-p-CF₃, R′ = i-Bu; 3b: R = C₆H₄-p-CF₃, R′ = t-Bu; 3c: R = C₆H₄-p-CF₃, R′ = Ph; 4a: R = C₆F₅, R′ = i-Bu; 4c: R = C₆F₅, R′ = Ph) in 81–98% yields. Molecular structures of the complexes except for 1a, 1c and 2a were determined by X-ray crystallography. Complex 1b has a square-planar structure with Pt–C(methyl) bonds of 2.083(8) and 2.109(8) Å, while the Pt–C(aryl) bonds of 2b–c, 3a–c, 4a and 4c (2.055(1)–2.073(8) Å) are shorter than them. Thermal decomposition of 1b, 2a–c, and 3a–c releases methane, biphenyl or 4,4′-bis(trifluoromethyl)biphenyl as the organic products, which are characterized by NMR spectroscopy. The solid product of the thermal reactions of 2b and 2c were characterized as the metallopolymers formulated as [Pt(PR′₂)₂]_n (5b: R′ = ^tBu; 5c: R′ = Ph), based on the solid-state NMR and elemental analyses.     

Crystal structures and magnetic properties of complexes of M(NO3)2; M = MnII,CoII, NiII,and CuII,with pyridine ligands carrying an aminoxyl radical

Four complexes of M(NO₃)₂(4NOPy-OMe)₂, (4NOPy-OMe = 4-(N-tert-butyloxylamino)-2-(methoxymethylenyl)pyridine, and M = Mn^II, 1; Co^II, 2; Ni^II, 3; Cu^II, 4), were prepared and fully characterized. X-ray single crystal analysis reveals that four complexes are isostructural. The molecular structures are distorted octahedral in which the methoxy oxygen atoms coordinate to the metal ion by trans-configuration while the pyridyl nitrogen atoms and the nitrate oxygen atoms coordinate by cis-configuration. The magnetic properties of all complexes were investigated by SQUID magneto/susceptometry. Temperature dependence of the molar magnetic susceptibilities in the temperature range of 2–300 K indicated that the magnetic coupling between aminoxyl radicals and metal ion was antiferromagnetic in the complex 1 and were ferromagnetic in the complexes 2–4. The quantitative analysis based on the spin Hamiltonian, H = −2J(S₁S_M + S_MS₂) yielded the best fit as J/k_B = −13.4 ± 0.1 K, g = 1.94 ± 0.002, and θ = −0.78 ± 0.02 K for the complex 1, J/k_B = 48.7 ± 2.1 K, g = 2.07 ± 0.02, and θ = −2.83 ± 0.41 K for the complex 3 (the data in the temperature range 300–50 K were used), and J/k_B = 57.0 ± 1.2 K, g = 2.002 ± 0.004, and θ = −9.8 ± 0.1 K for the complex 4.     

Synthesis and characterization of novel intramolecularly O,C,O-coordinated heteroleptic organostannylenes and their tungstenpentacarbonyl complexes

The syntheses are reported of the novel heteroleptic organostannylenes [2,6-(ROCH₂)₂C₆H₃]SnCl (1, R = Me; 2, R = t-Bu) and of their tungstenpentacarbonyl complexes [2,6-(ROCH₂)₂C₆H₃](X)SnW(CO)₅ (3, X = Cl, R = Me; 4, X = Cl, R = t-Bu; 5, X = H, R = Me). The compounds were characterized by means of elemental analyses, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopies, electrospray mass spectrometry and in case of 3 and 4 also by single crystal X-ray diffraction analysis. For the two latter compounds the substituents bound at the ether oxygen atom control the strength of intramolecular O → Sn coordination. Thus, the O–Sn distances amount to 2.391(5)/2.389(5) (3) and 2.464(3)/2.513(3) Å (4).     

Synthesis,structure and magnetic properties of pyrazolate-bridged dinuclear complexes [{M(NCS)(4-Phpy)}2(μ-bpypz)2] (M = Co2+ and Fe2+)

The synthesis and magnetic characterization of pyrazolato-bridged dinuclear complexes [{M(NCS)(4-Phpy)}₂(μ-bpypz)₂] (Hbpypz = 3,5-bis(2-pyridyl)-pyrazole; 4-Phpy = 4-phenylpyridine; M = Co²⁺ (1) and Fe²⁺ (2)) are described together with the X-ray crystal analysis of the cobalt complex. The structure of 1 shows that the desired coordination has been achieved with the cobalt atoms being coordinated to two bpypz to form the dimer. The X-ray diffraction patterns show 1 and 2 to be isomorphous at room temperature. 2 displays a single spin-crossover transition between the [HS–HS] and [LS–LS] states with T_c = 150 K.     

Structures and spectral properties of heteroleptic copper (I) complexes: A theoretical study based on density functional theory

The structures and electronic absorption spectra of newly synthesized heteroleptic copper (I) complexes [CuL₁L₂]⁺ (L₁ = phen-imidazole and/or L₂ = dipyrido [3,2-a:2’,3’-c] phenazine derivatives) are analyzed under the light of density functional theory (DFT) and time-dependent DFT (TD-DFT). The ground states geometries, characterized by π-stacking interactions, have been optimized using PBE-D functional taking into account dispersion correction. The UV-visible theoretical absorption spectra have been calculated using B3LYP functional in vacuum and taking into account solvent corrections by means of the polarized continuum model (PCM). Whereas the PBE-D functional is well adapted to the determination of the structures, it does underestimate drastically the transition energies. The spectra are characterized by high density of states, mainly metal-to-ligand-charge-transfer (MLCT) and intra-ligand (IL), between 600 nm and 250 nm. Most of the complexes show an intense band in the near-UV energy domain (～320 nm) corresponding to an IL transition. The lowest part of the absorption spectra, starting at 600 nm, corresponds to MLCT transitions leading to a shoulder observed experimentally between 400 and 500 nm. The upper part of the spectra, beyond 300 nm, puts in evidence strong mixing between ligand-to-ligand-charge-transfer (LLCT), IL and MLCT states.     

Long-distance electronic interaction in a molecular wire consisting of a ferrocenyl–ethynyl unit bridging two [(η5-C5H5)(dppe)M] metal centers

Several multinuclear ferrocenyl–ethynyl complexes of formula [(η⁵-C₅H₅)(dppe)M^II?CC–(fc)_n–CC–M^II(dppe)(η⁵-C₅H₅)] (fc = ferrocenyl; dppe = Ph₂PCH₂CH₂PPh₂; 1: M^II = Ru²⁺, n = 1; 2: M^II = Ru²⁺, n = 2; 3: M^II = Ru²⁺, n = 3; 4: M^II = Fe²⁺, n = 2; 5: M^II = Fe²⁺, n = 3) were studied. Structural determinations of 2 and 4 confirm the ferrocenyl group directly linked to the ethynyl linkage which is linked to the pseudo-octahedral [(η⁵-C₅H₅)(dppe)M] metal center. Complexes of 1–5 undergo sequential reversible oxidation events from 0.0 V to 1.0 V referred to the Ag/AgCl electrode in anhydrous CH₂Cl₂ solution and the low-potential waves have been assigned to the end-capped metallic centers. The solid-state and solution-state electronic configurations in the resulting oxidation products of [1]⁺ and [2]²⁺ were characterized by IR, X-band EPR spectroscopy, and UV–Vis at room temperature and 77 K. In [1]⁺ and [2]²⁺, broad intervalence transition band near 1600 nm is assigned to the intervalence transition involving photo-induced electron transfer between the Ru³⁺ and Fe²⁺ metal centers, indicating the existence of strong metal-to-metal interaction. Application of Hush’s theoretical analysis of intervalence transition band to determine the nature and magnitude of the electronic coupling between the metal sites in complexes [1]⁺ and [2]²⁺ is also reported. Computational calculations reveal that the ferrocenyl–ethynyl-based orbitals do mix significantly with the (η⁵-C₅H₅)(dppe)Ru metallic orbitals. It clearly appears from this work that the ferrocenyl–ethynyl spacers strongly contribute in propagating electron delocalization.