Mono Complexes Research Articles

Synthesis, characterization of cationic half-sandwich scandium mono(silylamide) complexes and their unexpected reactivity toward C–Cl σ bond activation of chlorobenzene

Treatment of the half-sandwich scandium bis(silylamide) complex (η5-C5Me5)Sc[N(SiMe3)2]2 with 1 equiv. of [PhNMe2H][B(C6F5)4] in THF and toluene gave the cationic half-sandwich scandium mono(silylamide) complexes [(η5-C5Me5)Sc{N(SiMe3)2}(THF)2][B(C6F5)4] (1) and [(η5-C5Me5)Sc{N(SiMe3)2}(PhNMe2)][B(C6F5)4] (2), respectively. 2 could be transformed into 1 by introducing of a small amount of THF. 2 was capable of activating kinetically inert C–Cl σ-bond of chlorobenzene to afford the cationic half-sandwich scandium chloride complex [{(η5-C5Me5)Sc(μ-Cl)(THF)2}2][B(C6F5)4]2 (3). 1–3 were characterization by elemental analysis and NMR spectroscopy. 1 and 3 were further structurally authenticated by X-ray crystallography.

Hydrogen-bonding interactions in a single-component molecular conductor: a hydroxyethyl-substituted radical gold dithiolene complex.

The anionic hydroxyethyl-substituted gold dithiolene complex [NEt4][Au(EtOH-thiazdt)2] is synthesized and further oxidized to the neutral radical species [Au(EtOH-thiazdt)2](•) through electrocrystallization. Single-crystal X-ray diffraction studies highlight the existence of the two cis and trans isomers for the monoanionic complex, with involvement of the hydroxy group in intermolecular O-H···S hydrogen-bonding interactions. The neutral radical complex, [Au(EtOH-thiazdt)2](•), is isostructural with its known ethyl analogue, namely, [Au(Et-thiazdt)2](•). It exhibits a semiconducting behavior (σRT = 0.05-0.07 S cm(-1)) at room temperature and ambient pressure with an activation energy of 0.14 eV. Comparison of the crystal structures and transport and magnetic properties with those of the prototypical [Au(Et-thiazdt)2](•) single-component conductor shows that the replacement of ethyl by a slightly bulkier hydroxyethyl substituent affects only weakly the overlap interactions, complemented here by added O-H···S hydrogen-bonding interactions.

Radical or not radical: compared structures of metal (M = Ni, Au) bis-dithiolene complexes with a thiazole backbone.

A complete series of dianionic, monoanionic, and neutral dithiolene complexes formulated as [Ni(Et-thiazdt)2](n), with n = -2, -1, 0, and Et-thiazdt: N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate, is prepared using an optimized procedure described earlier for the N-Me derivatives. Electrochemical and spectroscopic properties confirm the electron-rich character of the Et-thiazdt dithiolate ligand. The three complexes are structurally characterized by single-crystal X-ray diffraction. The paramagnetic anionic complex [Ni(Et-thiazdt)2](-1), as Ph4P(+) salt, exhibits side-by-side lateral interactions leading to a Heisenberg spin chain behavior. The solid-state structure of the neutral, diamagnetic [Ni(Et-thiazdt)2](0) complex shows a face-to-face organization with a large longitudinal shift, at variance with the structure of its radical and neutral gold dithiolene analogue described earlier and formulated as [Au(Et-thiazdt)2](•). Comparison of the two structures, and those of the other few structurally characterized pairs of Ni/Au dithiolene complexes, demonstrates the important role played by overlap interactions between gold dithiolene radical species. Despite its closed-shell character, the neutral nickel complex [Ni(Et-thiazdt)2](0) exhibits a semiconducting behavior with a room-temperature conductivity σRT ≈ 0.014 S cm(-1).

Complexation of mono- and dicationic surfactants with decanucleotide. Influence of the head group nature

Complexation of decanucleotide (GCGTTAACGC) with mono- and dicationic surfactants (hydrodynamic diameter of lipoplexes ≤200 nm) is accompanied by the compensatory change of electrokinetic potential from −54 to +50 mV. The complexation efficiency considerably increases with introduction of a hydroxyethyl fragment into the surfactant head group.

Synthesis, Structural, and Photophysical Studies of Phenylquinoline and Phenylquinolinyl Alkynyl Based Pt(II) Complexes

We present the synthesis, characterization, and photophysical properties of two series of alkynyl–platinum(II) complexes containing the phenylquinoline (Hpq) or the cyclometalated phenylquinolinyl (pq) ligand. Unusual monoanionic complexes (NBu4)[Pt(C≡CR)3(Hpq)] (R = Tol 1, C6H4OMe-3 2, C6H4CF3-4 3) were generated in moderate yield by treatment of [Pt(pq)(μ-Cl)]2 with an excess of LiC≡CR (1:8), followed by subsequent treatment with NBu4 in iPrOH. However, a similar reaction with LiC≡CtBu evolves with formation of [Pt(pq)(μ–κCα:η2-C≡CtBu)]2 4. Related dimers [Pt(pq)(μ–κCα:η2-C≡CR)]2 (R = Tol 5, C6H4OMe-3 6, C6H4CF3-4 7) were successfully prepared by modification of the reaction conditions. Single-crystal studies were performed on 2, 4, and 5, revealing the presence of intramolecular (H···Pt and H···C≡C) and intermolecular Omethoxy···HHpq contacts in 2 and the formation of butterfly structures in 4 and 5. In the tBu derivative 4, a shorter intramolecular Pt···Pt separation was found [3.0936(3) A in 4 vs 3.2...

Aluminum methyl and isopropoxide complexes with ketiminate ligands: Synthesis, structural characterization and ring-opening polymerization of cyclic esters

Mono(ketiminate) aluminum dimethyl complexes 1a–5a and bis(ketiminate) aluminum methyl complex 2b were synthesized via the reactions of AlMe3 with various N-aryl substituted ketimine compounds in a 1:1 or 1:2 molar ratio, respectively. The reaction of Al(OiPr)3 with the ketimine compound L2H resulted in a bis(ketiminate) aluminum isopropoxide complex 2c. All the complexes were characterized by 1H and 13C{1H} NMR spectroscopy, either EA or HRMS analysis. X-ray diffraction measurement of complexes 2a and 3a confirmed that in the solid state both 2a and 3a exist as a tetrahedron structure with the aluminum atom center surrounded by the oxygen and nitrogen donors of the bis-chelating ketiminate ligand as well as two methyl groups. Besides, a triligated aluminum complex 3 (Al(L3)3) with a six-coordinated metal core and a dinuclear aluminum isopropoxide complex 6d [(L6)2Al(μ-OiPr)2Al(OiPr)2] with C2-symmetry were isolated and characterized by X-ray diffraction studies. All aluminum methyl complexes behaved as active initiators in the ring-opening polymerization (ROP) of rac-lactide (rac-LA), affording isotactic-enriched polylactides (PLAs) with high molecular weights and broad molecular weight distributions at 70°C. The steric and electronic characters of the ancillary ligands show significant effects both on the activity and the stereoselectivity. The introduction of an electron-withdrawing group on the para-position of N-aryl ring of the ligand resulted in an increase of the catalytic activity. However, the electronic character of ancillary ligands showed a neglectable effect on the ROP of ε-CL initiated by these aluminum complexes. For both monomers, bis(ketiminate) aluminum complex 2b was found to be more active than the corresponding mono(ketiminate) complex 2a of the same ligand. Aluminum isopropoxide complex 2c exerted better control for the polymerizations of both monomers, providing polymers with narrower molecular weight distributions and smaller molecular weights which are comparable to the theoretical values

Charge-Delocalized κ2C,N-NHC-Amine Complexes of Rhodium, Iridium, and Ruthenium

The development of a novel set of complexes bearing an NHC-amine ligand (C-NHC-NH2) is described. M(cod) complexes (M = 1r, Rh) and a Ru complex have been synthesized in which three different coordination modes of the ligand were established: monodentate, neutral bidentate, and anionic bidentate. The anionic bidentate coordination mode of the anionic C-NHC-NH- ligand arises from deprotonation of the amine moiety of the neutral C-NHC-NH2 ligand. Ligand deprotonation proved to be reversible for the Rh and 1r complexes, as was shown by subsequent treatment of the complexes with base and acid. The structural parameters of these differently coordinated ligands were examined, and it was shown that the conjugation of the aniline ring plays a major role in determining the ligand properties. Structural parameters derived from DFT calculations confirm delocalization of the anionic charge over the ligand framework, as is clear from a comparison of the (hypothetical) neutral bidentate complexes [M(cod)(kappa C-2,N-{C-NHC-NH2})](+) with those of the (synthesized) monoanionic complexes [M(cod)(kappa C-2,N-{C-NHC-NH})] (M = Rh, Ir). A similar trend in the structure and bond lengths of the aniline rings was found in the solid-state structure of the novel dimeric complex [(Ru(kappa C-2,N-{C-NHC-NH})(kappa C-2,N-{C-NHC-NH2})Cl)2(mu-Cl)](PF6). The octahedral d5 ruthenium(III) centers in this complex both contain a neutral bidentate C-NHC-NH2 ligand as well as an anionic bidentate ligand. Quite remarkably, the complex is diamagnetic, arising from antiferromagnetic coupling of the two low-spin ruthenium(III) centers over the chloride linker. DFT calculations indeed confirm that the open-shell singlet electronic structure is most stable.

Substitution effect on the intermolecular halogen and hydrogen bonds of the σ‐bonded fluorinated pyridine···XY/HX complexes (XY = F2, Cl2, ClF; HX = HF, HCl)

Optimal structures, electronic and thermodynamic properties of the title complexes are presented. The stability of the hydrogen bonded systems is enhanced by the increasing dipole moments whereas in the halogen bonded systems it is also affected by the atom size in the diatomics. The consecutive addition of fluorine atoms to the pyridine moiety results in the decrease of the interaction energy for both types of the investigated bonds. The substitution on the meta sites in pyridine leads to more stable complexes than the substitution in the ortho position. The role of substitution on electric polarization and electrostatic forces is estimated by the symmetry‐adapted perturbation theory energy decomposition. The predicted Gibbs free energies of the complexes of mono fluorinated pyridines with HCl, HF, and ClF are from −12 to −22 kJ mol−1 at 200 K. The possible experimental identification of the complexes with respect to the vibrational modes is discussed. © 2014 Wiley Periodicals, Inc.

Copper(II) and zinc(II) complexes of mono- and tri-linked azacrown macrocycles: Synthesis, characterization, X-ray structure, phosphodiester hydrolysis and DNA cleavage

A new tri-linked azacrown macrocycle (L2) was synthesized from mono macrocycle analogue (L1) by Williamson etherification and characterized by FT-IR, 1H NMR, 13C NMR, DEPT 13C NMR, MS, and elemental analysis. The reaction of copper(II) and zinc(II) salts yielded corresponding complexes and formulated as CuL1Cl2 (1), CuL1(NO3)2·3H2O (2), Cu2L2(NO3)4·4H2O (3), ZnL1(OAc)2 (4) and Zn3L2(OAc)6·3H2O (5). Mono and trinuclear zinc(II) complexes 4 and 5, respectively, have been tested as catalysts for hydrolysis of 2-hydroxylpropyl-4-nitrophenyl phosphate (HNPP). At pH 8.5 the mononuclear complex 4 was found to be inactive. In contrast, trinuclear complex 5 was hydrolyzing phosphodiester and the reaction was up to 35-fold faster than the unpromoted reaction. Mono and dinuclear copper(II) complexes 2 and 3 cleave plasmid pG2 DNA by using an oxidative mechanism under aerobic conditions. Dinuclear copper(II) complex 3 showed a much higher cleavage efficiency than its mononuclear analogue 2 at the same Cu2+ concentration. The X-ray structure of 1 is reported. In this complex, the Cu(II) is bound by three amine nitrogens from the macrocyclic ligand L1 and two chloride anions as distorted trigonal bipyramidal geometry.

Mono and dinuclear copper(II) naproxenato complexes containing 3-picoline and 4-picoline: synthesis, structure, properties, catechol oxidase, and antimicrobial activities

Mononuclear and dinuclear copper(II) complexes [Cu2(μ-nap)4(3-pic)2] (1) and [Cu(nap)2(H2O)(4-pic)2] (2) have been synthesized in the presence of 3-picoline and 4-picoline. Two complexes were characterized by FT-IR, UV–vis spectroscopic methods and their thermal stabilities were determined by TG/DTA/DTG techniques. The crystal structures of 1 and 2 were established by X-ray analysis. X-ray structure analysis has shown that copper(II) has a distorted square-pyramidal geometry. Naproxenate is a bridging ligand in 1 and monodentate in 2. Two complexes have shown catalytic activity on oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone exhibiting saturation kinetics at high substrate concentrations. The complexes were also screened for antimicrobial activity against pathogenic bacteria and fungi. The complexes exhibited antimicrobial activity against Entrococcus faecalis and Candida albicans.

Coordination chemistry of sterically encumbered pyrrolyl ligands to chromium(II): mono(pyrrolyl)chromium and diazachromocene formation.

A series of diazachromocenes with sterically demanding pyrrolyl ligands, 2,5-(Me3C)2C4H2N (1), 2,5-(Me3C)2-3,4-Me2C4N (2) and 2,3,5-(Me3C)3C4HN (3), was prepared and investigated by various spectroscopic techniques, and in some cases by X-ray diffraction and magnetic susceptibility studies. The diazachromocenes exhibit an S = 1 ground state; no indication of a spin-equilibrium was obtained. With the same ligands mono(pyrrolyl)chromium(II) complexes are accessible, [{(κN-2,5-(Me3C)2C4H2N)Cr(thf)}2(μ-Cl)2] (1-CrCl(thf)), [(κN-2,5-(Me3C)2-3,4-Me2-C4H2N)Cr(Cl)(tmeda)] (2-CrCl(tmeda) and [(η(5)-2,3,5-(Me3C)3C4HN)Cr(μ-Cl)2] (3-CrCl), which show either η(5)- or η(1)-(κN) coordination depending on the substitution pattern. (1)H NMR spectroscopy serves as a valuable tool to distinguish between these coordination modes. The Cr(II) atoms in the mono(pyrrolyl) complexes adopt a high spin configuration (S = 2) and in dimeric species antiferromagnetic coupling between the spin carriers was observed. However, none of these mono(pyrrolyl)chromium complexes is an effective or selective ethylene oligomerization catalyst on activation with MAO or AlMe3, supporting the importance of a Cr(I)/Cr(III)-based catalytic cycle.

Decoding the patterns of ubiquitin recognition by ubiquitin-associated domains from free energy simulations

Ubiquitin is a highly conserved, highly represented protein acting as a regulating signal in numerous cellular processes. It leverages a single hydrophobic binding patch to recognize and bind a large variety of protein domains with remarkable specificity, but can also self-assemble into chains of poly-diubiquitin units in which these interfaces are sequestered, profoundly altering the individual monomers' recognition characteristics. Despite numerous studies, the origins of this varied specificity and the competition between substrates for the binding of the ubiquitin interface patch remain under heated debate. This study uses enhanced sampling all-atom molecular dynamics to simulate the unbinding of complexes of mono- or K48-linked diubiquitin bound to several ubiquitin-associated domains, providing insights into the mechanism and free energetics of ubiquitin recognition and binding. The implications for the subtle tradeoff between the stability of the polyubiquitin signal and its easy recognition by target protein assemblies are discussed, as is the enhanced affinity of the latter for long polyubiquitin chains compared to isolated mono- or diubiquitin.

Varying electronic structural forms of ruthenium complexes of non-innocent 9,10-phenanthrenequinonoid ligands

Bis(acetylacetonato)ruthenium complexes [Ru(acac)2(Q1-3)], 1-3, incorporating redox non-innocent 9,10-phenanthrenequinonoid ligands (Q1 = 9,10-phenanthrenequinone, 1; Q2 = 9,10-phenanthrenequinonediimine, 2; Q3 = 9,10-phenanthrenequinonemonoimine, 3) have been characterised electrochemically, spectroscopically and structurally. The four independent molecules in the unit cell of 2 are involved in intermolecular hydrogen bonding and π-π interactions, leading to a 2D network. The oxidation state-sensitive bond distances of the coordinated ligands Q(n) at 1.296(5)/1.289(5) Å (C-O), 1.315(3)/1.322(4) Å (C-N), and 1.285(3)/1.328(3) Å (C-O/C-N) in 1, 2 and 3, respectively, and the well resolved (1)H NMR resonances within the standard chemical shift range suggest DFT supported variable contributions from valence formulations [Ru(III)(acac)2(Q˙(-))] (spin-coupled) and [Ru(II)(acac)2(Q(0))], respectively. Complexes 1-3 exhibit one oxidation and two reduction steps with comproportionation constants Kc∼ 10(7)-10(22) for the intermediates. The electrochemically generated persistent redox states 1(n) (n = 0, 1-, 2-) and 2(n)/3(n) (n = 1+, 0, 1-, 2-) have been analysed by UV-vis-NIR spectroelectrochemistry and by EPR for the paramagnetic intermediates in combination with DFT and TD-DFT calculations, revealing significant differences in the oxidation state distribution at the {Ru-Q} interface for 1(n)-3(n). In particular, the diminished propensity of the NH-containing systems for reduction results in the preference for Ru(II)(Q(0)) relative to Ru(III)(Q˙(-)) (neutral compounds) and for Ru(II)(Q˙(-)) over the Ru(III)(Q(2-)) alternative in the case of the monoanionic complexes.

ReI–IrI bimetallic complexes based on a bis(chelating) ligand composed of 1,10-phenanthroline and N-heterocyclic carbene: Coordination chemistry and their application for optical indicator of CO gas

Mono complex [Cl(CO)3ReI(IL-2)](PF6) and bimetallic complexes Cl(CO)3ReI(IL-2)–IrI(Ligand)nCl, where IL-2=1,3-dimethyl-2,3-dihydro-1H-imidazo[4,5-f][1,10]phenanthroline-2-yl and Ligand=1,5-cyclooctadiene (n=1) or carbon monoxide (n=2), were synthesized, characterized, and applied to react with carbon monoxide. Bis(chelating) ligand, IL-2, has two coordinating sites, 1,10-phenanthroline and imidazolium moieties. These complexes display typical intraligand transition (π–π∗) and metal-to-ligand charge-transfer (MLCT) bands in the ultraviolet and visible regions, respectively. It was demonstrated that complex Cl(CO)3ReI(IL-2)–IrI(COD)Cl can be used as a carbon monoxide (CO) indicator because Cl(CO)3ReI(IL-2)–IrI(CO)2Cl, a CO-substituted bimetallic complex, displays distinct optical behaviors compared to those of Cl(CO)3ReI(IL-2)–IrI(COD)Cl.

Zirconium Complexes of Two Different Iminopyrrolyl Ligands – Syntheses and Structures

AbstractThe reaction involving N‐aryliminopyrrolyl ligand, 2‐((p‐Me‐C6H3N=CMe)–C4H3NH) (1a) (ImpMe‐H), and Zr(OtBu)4 in a 2:1 molar ratio in toluene at 90 °C afforded the corresponding bis(iminopyrrolyl) complex of zirconium, [(ImpMe)2Zr(OtBu)2] (2a) having two bidentate iminopyrrole groups in the coordination sphere. In contrast, the bulkier 2‐((2,6‐iPr2C6H3N=CH)–C4H3NH) (1b) (ImpDipp‐H) and Zr(OtBu)4 in a 1:1 molar ratio under the same condition yielded the corresponding mono(iminopyrrolyl) complex of zirconium, [(ImpDipp)Zr(OtBu)3(THF)] (2b), which contains only one bidentate iminopyrrole moiety in the coordination sphere. Both complexes were characterized by single‐crystal X‐ray diffraction analysis. The solid‐state structures reveal that the bulky iminopyrrole ligands cause a steric crowding around the zirconium ion along with three tert‐butoxide ligands attached to the central metal atom.

Aminopyridinate–FI Hybrids, Their Hafnium and Titanium Complexes, and Their Application in the Living Polymerization of 1‐Hexene

Based on two well-established ligand systems, the aminopyridinato (Ap) and the phenoxyimine (FI) ligand systems, new Ap-FI hybrid ligands were developed. Four different Ap-FI hybrid ligands were synthesized through a simple condensation reaction and fully characterized. The reaction of hafnium tetrabenzyl with all four Ap-FI hybrid ligands exclusively led to mono(Ap-FI) complexes of the type [(Ap-FI)HfBn2 ]. The ligands acted as tetradentate dianionic chelates. Upon activation with tris(pentafluorophenyl)borane, the hafnium-dibenzyl complexes led to highly active catalysts for the polymerization of 1-hexene. Ultrahigh molecular weights and extremely narrow polydispersities support the living nature of this polymerization process. A possible deactivation product of the hafnium catalysts was characterized by single-crystal X-ray analysis and is discussed. The coordination modes of these new ligands were studied with the help of model titanium complexes. The reaction of titanium(IV) isopropoxide with ligand 1 led to a mono(Ap-FI) complex, which showed the desired fac-mer coordination mode. Titanium (IV) isopropoxide reacted with ligand 4 to give a complex of the type [(ApH-FI)2 Ti(OiPr)2 ], which featured the ligand in its monoanionic form. The two titanium complexes were characterized by X-ray crystal-structure analysis.

Investigation on the effect of Tb(dbm)3phen on the luminescent properties of Eu(dbm)3phen-containing mesoporous silica nanoparticles

Eu(dbm)3phen and Tb(dbm)3phen complexes (tris(dibenzoylmethane) mono(1,10-phenantroline) Ln(III)) were impregnated in ordered mesoporous silica nanoparticles (MSNs) with an average size of 50–70 nm and a pore diameter centred at 2.8 nm, with the aim of increasing the luminescence by avoiding concentration quenching and having mainly in mind the application as down-shifter for multi-crystalline solar cells. The morphological, structural, textural and luminescent properties of the synthesized samples were characterized by N2 adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–visible spectroscopy and photoluminescence measurements. It is demonstrated that inclusion in the MSNs allows one to use much higher loadings (23 wt%) of the Eu-complex than in other matrices, and that co-doping with Tb(dbm)3phen improves luminescence for samples with Eu(dbm)3phen content lower than about 10 wt%. Results are interpreted by using a simple sphere of action model adapted to the case of a pore-limited system.

Synthesis and Characterization of Platinum(II) Complexes Containing Spiro System

Platinum complexes [Pt(bpy)Cl2](bpy: 2,2'-bipyridine) and [Pt(PT)Cl2](PT: 1,10-phenantroline) were reacted with 5,5"-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(2,2'-bipyrine), bpy-spiro-bpy, to afford mono and diplatinium complexes: [(bpy)Pt(bpy-spiro-bpy)][PF6]2, [(bpy)Pt(bpy-spiro-bpy)Pt(bpy)])[PF6]4, and [(PT)Pt(bpy-spiro-bpy)])][PF6]2, which were characterized by NMR, UV/VIS, mass spectrum, and PL spectroscopy. They showed very high internal quantum yields (0.35-0.67) and emitted light in the blue region (473-520 nm). Herein, we describe the synthesis, characterization of the mono- and di-platinum complexes in detail.

Synthesis and Structural Characterization of Lithium, Potassium, Magnesium, and Heavier Group 14 Metal Complexes Derived from 2-Quinolyl-Linked (Thiophosphorano)methane

The synthesis and structural characterization of lithium, magnesium, potassium, and a series of low-valent group 14 metal compounds derived from the novel 2-quinolyl-linked phosphoranosulfide CH2(iPr2P═S)(C9H6N-2) (3) are reported. The monoanionic thiophosphinoyl lithium complex [Li(Et2O){CH(iPr2P–S)(C9H6N-2)}]2 (4) and magnesium complex [Mg{CH(iPr2P–S)(C9H6N-2)}2] (5) have been prepared from the reaction of 3 with 1 equiv of nBuLi or 0.5 equiv of nBu2Mg in THF. Metathesis of 4 with 2 equiv of KtBuO afforded the corresponding polymeric thiophosphinoyl potassium complex [K{CH(iPr2P–S)(C9H6N-2)}]n (6). The metathesis reaction of 4 with GeCl2·(dioxane) and PbCl2 afforded the “open-box” 1,3-digermacyclobutane [Ge{μ2-C(iPr2P═S)(C9H6N-2)]2 (9) and “twisted-step” 1,3-diplumbacyclobutane [Pb{μ2-C(iPr2P═S)(C9H6N-2)]2 (10), respectively. Reaction of 3 with 1 equiv of M{N(SiMe3)2}2 (M = Sn, Pb) afforded the corresponding “open-box” 1,3-distannacyclobutane [Sn{μ2-C(iPr2P═S)(C9H6N-2)]2 (11) and [Pb{μ2-C(iPr2P═S)(C9H6N...

Long-Range Intramolecular Electronic Communication in Bis(ferrocenylethynyl) Complexes Incorporating Conjugated Heterocyclic Spacers: Synthesis, Crystallography, and Electrochemistry

A new series of bis(ferrocenylethynyl) complexes, 3-7, and a mono(ferrocenylethynyl) complex, 8, have been synthesized incorporating conjugated heterocyclic spacer groups, with the ethynyl group facilitating an effective long-range intramolecular interaction. The complexes were characterized by NMR, IR, and UV-vis spectroscopy as well as X-ray crystallography. The redox properties of these complexes were investigated using cyclic voltammetry and spectroelectrochemistry. Although there is a large separation of ∼14 Å between the two redox centers, ΔE(1/2) values in this series of complexes ranged from 50 to 110 mV. The appearance of intervalance charge-transfer bands in the UV-vis-near-IR region for the monocationic complexes further confirmed effective intramolecular electronic communication. Computational studies are presented that show the degree of delocalization across the Fc-C≡C-C≡C-Fc (Fc = C5H5FeC5H4) highest occupied molecular orbital.