Diimine Complexes Research Articles

TRISPHAT salts. Efficient NMR chiral shift and resolving agents for substituted cyclometallated ruthenium bis(diimine) complexes

The determination of the enantiomeric purity of monocationic ruthenium(II) cyclometallated complexes is easily carried out by 1H-NMR analysis using a TRISPHAT salt as a diamagnetic chiral shift reagent. Resolution of the organometallic complexes can be conveniently carried by preparative thin layer chromatography using TRISPHAT as a chiral counter-ion.

Dimerization–Carbostannylation of Alkynes Catalyzed by a Palladium–Diimine Complex: Regioselectivity, Stereoselectivity and Mechanism

Abstract Double insertion of alkynes into the C–Sn bond of an alkynyl-, alkenyl-, allyl- or arylstannane proceeded in the presence of a palladium–diimine complex to afford highly conjugated alkenylstannanes with exclusive syn selectivity. Perfect regioselectivities were observed in the dimerization–carbostannylation of ethyl propiolate with a palladium–1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene complex, which allowed regio- and stereoselective synthesis of stannyl-substituted muconic acid derivatives. The π-conjugation of the dimerization–carbostannylation products was further extended through a cross-coupling or homocoupling reaction. A palladacyclopentadiene is proposed as an intermediate species.

Molecular structure determination of Ni(II) diimine complex and DMA analysis of Ni(II) diimine‐based polyethenes

AbstractDynamic mechanical thermoanalysis showed that polyethene, prepared under suitable polymerization conditions with the Brookhart‐type catalyst dibromo‐N,N′‐1,2‐acenaphthylenediylidenebis[2,6‐bis(1‐methylethyl)benzeneamine]Ni(II)/methylaluminoxane (MAO), behaved like an elastomer, even though no comonomer was added. A structural characterization showed that the polymers contained methyl to hexyl branches and some longer branches. The effect of the polymerization conditions on branching was investigated through variations in the pressure and temperature of the polymerization. Depending on the degree and type of branching, polyethene was either quite amorphous or highly crystalline with a high melting temperature. The solid‐state structure of the catalyst dibromo‐N,N′‐1,2‐acenaphthylenediylidenebis[2,6‐bis(1‐methylethyl)benzeneamine]Ni(II) consisted of two centrosymmetrically related monomeric moieties, where Ni atoms were bridged by two bromide ligands. The Ni atom was five‐coordinated, with a square pyramidal coordination polyhedron. The sixth coordination site of the octahedral geometry was effectively blocked by the isopropyl groups of the 2,6‐C6H3(i‐Pr) substituents of the diimine ligand. In solution in the presence of MAO, the longer bridging NiBr bonds broke, and the complex dissociated to a monomeric species. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1426–1434, 2001

Computer-aided design (CAD) of Mn(II) complexes: superoxide dismutase mimetics with catalytic activity exceeding the native enzyme.

New Mn(II) macrocyclic pentaamine complexes derived from the biscyclohexyl-pyridine complex, M40403 ([manganese(II)dichloro[(4R,9R,14R,19R)-3,10,13,20,26-pentaazatetracyclo[20.3.1.0.(4,9)0(14,19)]hexacosa-1(26),-22(23),24-triene]]), are described here. The complex M40403 was previously shown to be a superoxide dismutase (SOD) catalyst with rates for the catalytic dismutation of superoxide to oxygen and hydrogen peroxide at pH = 7.4 of 1.2 x 10(+7) M(-1) s(-1).(1) The use of the computer-aided design paradigm reported previously for this class of Mn(II) complexes(2,3) led to the prediction that the 2S,21S-dimethyl derivative of M40403 should possess superior catalytic SOD activity. The synthesis of this new macrocyclic Mn(II) complex, [manganese(II)dichloro[2S, 21S-dimethyl-(4R,9R,14R,19R)-3,10,13,20,26-pentaazatetracyclo[20.3.1.0.(4,9)0(14,19)]hexacosa-1(26),22(23),24-triene]], 5, was accomplished via a high yield template condensation utilizing the linear tetraamine, N,N'-Bis[(1R,2R)-[2-(amino)]cyclohexyl]-1,2-diaminoethane, 1, 2,6-diacetylpyridine, and MnCl(2) to form the macrocyclic diimine complex, 2, which then is reduced. The two other possible dimethyl diastereomers of 5 (2R,21R-dimethyl,3, and 2R,21S-dimethyl, 6) were also prepared via reduction of the diimine complex 2. Two of these complexes, 3 and 5, were characterized by X-ray structure determination confirming their absolute stereochemistry as 2R,21R-dimethyl and 2S,21S-dimethyl, respectively. The results of the MM calculations which predict that the 2S,21S-dimethyl complex, 5, should be a high activity catalyst and that the 2R,21R-dimethyl complex, 3, should have little or no catalytic activity are presented. The catalytic SOD rates for these complexes are reported for each of these complexes and a correlation with the modeling predictions is established showing that 2R,21R-complex, 3, has no measurable catalytic rate, while the 2R,21S complex, 6, is identical to M40403, and the 2S,21S- complex, 5, possesses a very fast rate at pH = 7.4 of 1.6 x 10(+9) M(-1) s(-1) exceeding that of the native mitochondrial MnSOD enzymes.

Syntheses and Structural Characterization of Luminescent Platinum(II) Complexes Containing Di-tert-butylbipyridine and New 1,1-Dithiolate Ligands

Three new di-tert-butylbipyridine (dbbpy) complexes of platinum(II) (1-3) containing 1,1-dithiolate ligands have been synthesized and characterized. The 1,1-dithiolates are 2,2-diacetylethylene-1,1-dithiolate (S(2)C=C(C(O)Me)2) (1), 2-cyano-2-p-bromophenylethylene-1,1-dithiolate (S(2)C=C(CN)(p-C(6)H(4)Br)) (2), and p-bromophenyl-2-cyano-3,3-dithiolatoacrylate (S(2)C=C(CN)(COO-p-C(6)H(4)Br)) (3). Complex 1 exhibits a solvatochromic charge-transfer absorption in the 430-488 nm region of the spectrum and a luminescence around 635 nm in ambient temperature CH(2)Cl(2) solution. These observations are consistent with what has been seen previously in related Pt diimine 1,1-dithiolate complexes. The nature of the emissive state is assigned as a (3)(mixed metal/dithiolate-to-diimine) charge transfer, while the solvatochromic absorption band corresponds to the singlet transition of similar orbital character. The other complexes also exhibit a low-energy solvatochromic absorption. The crystal structures of two of the complexes have been determined, representing the first time that Pt(diimine)(1,1-dithiolate) complexes have been crystallographically studied. The structures confirm the expected square planar coordination geometry with distortions in bond angles dictated by the constraints of the chelating ligands. The Pt-S and Pt-N bond lengths and S-Pt-S and N-Pt-N bond angles for the two structures are identical within experimental error (2.283(2) and 2.278(2) A; 2.053(6) and 2.050(8) A; 75.01(8) degrees and 75.40(8) degrees; 79.2(2) degrees and 79.0(2) degrees, respectively). Crystal data for 1: monoclinic, space group P2(1)/n (No. 14), with a = 7.20480(10) A, b = 20.53880(10) A, c = 19.1072(2) A, beta = 93.83 degrees, V = A(3), Z = 4, R1 = 3.34% (I > 2sigma(I)), wR2 = 9.88% (I > 2sigma(I)) for 3922 unique reflections. Crystal data for 2: monoclinic, space group P2(1)/n (No. 14), with a = 15.0940(5) A, b = 9.5182(3) A, c = 20.4772(7) A, beta = 111.151(1) degrees, V = A(3), Z = 4, R1 = 4.07% (I > 2sigma(I)), wR2 = 8.64% (I > 2sigma(I)) for 3859 unique reflections.

Ethylene oligomerization by cobalt(II) diimine complexes/EAO

The catalytic properties of a series of Co(II) diimine complexes Co( N ∧ N)Cl 2 ( A: N ∧ N= N, N′- o-phenylenebisbenzal; B: N ∧ N= N, N′-ethylenebisbenzal; C: N ∧ N= N, N′- o-phenylenebis(diphenylmethylene)) in combination with ethylaluminoxane (EAO) as cocatalyst for ethylene oligomerization have been investigated. Treatment of the cobalt(II) diimine complexes with EAO in toluene generated active catalysts in situ that are capable of oligomerizing ethylene to low-carbon olefins. The catalytic activity and product distribution were affected by reaction conditions, such as reaction temperature, the ratios of Al/Co and the reaction time. The activity of 1.30×10 5 g oligomers/mol Co h for the catalytic system of CoCl 2(Ph 2C o-NC 6H 4NCPh 2) with EAO at 200°C was observed, with the selectivity of 94.4% to C 4–10 olefins and 87.2% to C 4–10 linear α-olefins.

Synthesis of a linear-shaped tetramer and trimers of rhenium(i) diimine complexes

First examples of a linear-shaped tetramer and non-symmetrical trimers of rhenium(I) diimine complexes have been synthesized in good yields, and their UV–vis absorption and emission spectra are reported.

A remarkable temperature-dependent, accidental degeneracy of 31P NMR chemical shifts in Ru(II) diphosphine/diimine complexes.

Several cis-RuX2((R)-BINAP)(diimine) complexes have been prepared, and many of these exhibit an unusual temperature-dependent, accidental degeneracy of the 31P shifts in their solution NMR spectra.

ChemInform Abstract: Platinum Diimine Complexes: Towards a Molecular Photochemical Device

Abstract Complexes having the general formula PtX2(diimine) where X2=dithiolate, bis(acetylide) and diimine=bipyridine, phenanthroline and derivatives have been investigated for potential use as chromophores in the conversion of light-to-chemical energy. These complexes, like the analogous X=CN systems, are luminescent in fluid solution. Previous studies of the dithiolate derivatives reveal that they possess a charge transfer excited state involving a mixed metal–dithiolate donor orbital and a π*(diimine) acceptor function with excited state properties including emission energies, lifetimes and redox potentials that are tunable by ligand variation. The bis(acetylide) complexes are brightly luminescent in fluid solution, and their excited state is shown to be MLCT in character, consistent with an earlier proposal. Both sets of diimine complexes show evidence of self-quenching, and for Pt(phen)(CCPh)2, weak excimer emission is observed. The mechanism of quenching has been probed through cross-quenching experiments and is thought to involve Pt⋯Pt interactions. Efforts are now focussing on the use of the PtX2(diimine) chromophores in dyads and triads with the goal of constructing a molecular photochemical device for light-to-chemical energy conversion. Connection of the Pt diimine chromophores to both a donor or reductive quencher and an acceptor is envisioned through new ligand bridges currently being synthesized using Pd-catalyzed coupling reactions and carbonyl condensations.

Synthesis, emission, and electrochemical properties of luminescent dinuclear zinc(II) chalcogenolate complexes. Dynamic 1H NMR studies and X-ray crystal structure of [(bpy)Zn2(SC6H4-Cl-p)(mu-SC6H4-Cl-p)(mu-OAc)2

A series of novel luminescent dinuclear zinc(II) diimine complexes with bridging chalcogenolate ligands have been synthesized, in which the two zinc atoms were found to exist in different coordination environment. The luminescence and electrochemical behavior of these complexes have been studied. These complexes have also been shown to exhibit dynamic fluxional behavior in solution due to an exchange of the bridging and terminal thiolate ligands. The mechanism and kinetics of which have been investigated by variable-temperature 1H NMR studies. The X-ray crystal structure of [(bpy)Zn2(SC6H4-Cl-p)(mu-SC6H4-Cl-p)(mu-OAc)2] has also been determined.

A novel type of metal-containing polyimides based on tricarbonylrhenium(I) diimine complexes

A series of rhenium containing polyimides was prepared by the polymerization between a tricarbonylrhenium diimine complex with various aromatic dianhydrides. Electronic absorption spectra of the polymers showed a very strong intramolecular charge transfer transition which obscures the transfer transition band due to the rhenium complex in the visible region. A large photocurrent response was also observed when the polyimide was irradiated at 514 nm.

Ethylene oligomerization by diimine iron(II) complexes/EAO

The catalytic properties of a series of Fe(II) diimine complexes (diimine= N, N′- o-phenylenebis(salicylideneaminato), N, N′-ethylenebis(salicylideneaminato), N, N′- o-phenylenebisbenzal, N, N′-ethylenebisbenzal) in combination with ethylaluminoxane (EAO) for ethylene oligomerization have been investigated. Treatment of the iron(II) complexes with EAO in toluene generates active catalytic systems in situ that oligomerize ethylene to low-carbon olefins. The effects of reaction temperature, ratios of Al/Fe and reaction periods on catalytic activity and product distribution have been studied. The activity of complex FeCl 2(PhCH o-NC 6H 4NCHPh) with EAO at 200°C is 1.35×10 5 g oligomers/mol Fe·h, and the selectivity of C 4–10 olefins is 84.8%.

Lowest electronic excited states of platinum(II) diimine complexes.

Absorption and emission spectra of Pt(diimine)L2 complexes (diimine = 2,2'-bipyridine (bpy) or 4,4'-dimethyl-2,2'-bipyridine (dmbpy); L = pyrazolate (pz-), 3,5-dimethylpyrazolate (dmpz-), or 3,4,5-trimethylpyrazolate (tmpz-)) have been measured. Solvent-sensitive absorption bands (370-440 nm) are attributed to spin-allowed metal-to-ligand charge-transfer (1MLCT) transitions. As solids and in 77 K glassy solution, Pt(bpy)(pz)2 and Pt(dmbpy)(pz)2 exhibit highly structured emission systems (lambda max approximately 494 nm) similar to those of the diprotonated forms of these complexes. The highly structured bands (spacings 1000-1400 cm-1) indicate that the transition originates in a diimine-centered 3(pi-->pi*) (3LL) excited state. The intense solid-state and 77 K glassy solution emissions from 3MLCT[d(Pt)-->pi*(bpy)] excited states of complexes with dmpz- and tmpz- ligands occur at longer wavelengths (lambda max = 500-610 nm), with much broader vibronic structure. These findings are consistent with increasing electron donation of the pyrazolate ligands, leading to a distinct crossover from a lowest 3LL to a 3MLCT excited state.

Syntheses, Crystal Structure, and Photochromic Properties of Rhenium(I) Complexes Containing the Spironaphthoxazine Moiety

A series of novel spironaphthoxazine-containing rhenium(I) tricarbonyl diimine complexes, which show interesting photoluminescence behavior involving intramolecular photosensitization, have been sy...

Distinction and quantitation of leucine-isoleucine isomers and lysine-glutamine isobars by electrospray ionization tandem mass spectrometry (MS(n), n = 2, 3) of copper(II)-diimine complexes.

Electrospray ionization of mixtures of isomeric and isobaric amino acids was investigated with the goal of distinguishing and quantifying the components. Isomeric amino acids leucine and isoleucine were readily distinguished and quantified in 90 : 10 to 10 : 90 binary mixtures using two-stage (MS(2)) and three-stage (MS(3)) tandem mass spectrometric dissociations of ternary Cu(2+)-2, 2'-bipyridyl (bpy) complexes, [Cu(AA - H)bpy](+). The complexes self-assembled in solution upon mixing the components and provided a convenient means of efficient derivatization that increased the efficiency of amino acid ionization by electrospray and shifted the mass of the analytes to a region which was free of solvent interferences. Low-energy dissociations of [Cu(AA - H)bpy](+) complexes in a quadrupole ion trap were achieved at >90% conversions and >80% trapping efficiencies for the MS(2) and MS(3) precursor and fragment ions. Isobaric amino acids glutamine and lysine were also distinguished through MS(2) and MS(3) of their ternary complexes with Cu(2+) and bpy. ESI of [Cu(Gln - H)bpy](+) was enhanced in the presence of [Cu(Lys - H)bpy](+), which resulted in non-linear response at low Lys concentrations.

Molecular Nonlinear Optical Properties of Acceptors Substituted 2,2′-Bipyridine and 1,10-Phenathroline Complexes of Nickel Dithiolate

Linear and nonlinear optical properties of two new nickel(diimine)(dithiolate) complexes, nickel(4,4′-dinitro2,2′-bipyridyl)(tfd), Ni(NO2bipy)(tfd), (tfd = 1,2-trifluoromethylethene-1,2-dithiolate) and nickel(4,7-diphenyl-1,10-phenathroline)(tfd), Ni(dpphen)(tfd) are reported. Ni(NO2bipy)(tfd) has a potent electronic acceptor substituted on the diimine ligand and exhibits an enhanced molecular first hyperpolarizability (β0 = −31 × 10−30 esu), which is more than three times greater than that (β0 = −10 × 10−30 esu) of Ni(dpphen)(tfd). Ni(NO2bipy)(tfd) also possesses the longest absorption wavelength, the largest solvatochromic shift, and one of the largest dipole moment changes (-16 debye from ground to excited state) among nickel(diimine)(dithiolate) complexes. Crystal X-ray structure of Ni(NO2bipy)(tfd) is used to compared the π-bonding structure of central (N=C-C=N)Ni(S-C=C-S) unit with that of previously known nickel(4,4′-bis(butyloxycarbonyl)-2,2′-bipyridyl)(tfd), Ni(CO2Bubipy)(tfd).

Platinum Diimine Bis(acetylide) Complexes: Synthesis, Characterization, and Luminescence Properties

A new set of luminescent platinum(II) diimine complexes has been synthesized and characterized. The anionic ligands in these complexes are arylacetylides. The complexes are brightly emissive in fluid solution with relative emission quantum yields phiem ranging from 3 x 10(-3) to 10(-1). Two series of complexes have been investigated. The first has the formula Pt(Rphen)(C...CC6H5)2 where Rphen is 1,10-phenanthroline substituted in the 5-position with R = H, Me, Cl, Br, NO2, or C...CC6H5, while the second has the formula Pt(dbbpy)(C=CC6H4X)2 where dbbpy = 4,4'-di(tert-butyl)bipyridine and X = H, Me, F, or NO2. From NMR, IR, and electronic spectroscopies, all of the complexes are assigned a square planar coordination geometry with cis-alkynyl ligands. The crystal structure of Pt(phen)(Ce-CC6H4CH3)2 confirms this assignment. All of the complexes exhibit an absorption band at ca. 400 nm that corresponds to a Pt d-->pi*diimine charge-transfer transition. The variation of lambdamax for this band with substituent variation supports this assignment. From similar changes in the energy of the solution luminescence as a function of substituents R and X, the emissive excited state is also of MLCT origin, but with spin-forbidden character on the basis of excited-state lifetime measurements (0.01-5.6 micros). The complexes undergo electron-transfer quenching, showing good Stern-Volmer behavior using 10-methylphenothiazine and N,N,N',N'-tetramethylbenzidine as reductive quenchers. Excited-state reduction potentials are estimated on the basis of a simple thermochemical analysis. Crystal data for Pt(phen)(C...CC6H4CH3)2: monoclinic, space group C2/c, a = 19.0961(1) A, b = 10.4498(1) A, c = 11.8124(2) A, beta = 108.413(1) degrees, V = 2236.49 A3, number of reflections 1614, number of variables 150, R1 = 0.0163, wR2 (I > 2sigma) = 0.0410.

Synthesis, structure, luminescence, and electrochemical properties of polynuclear mercury(II) chalcogenolate complexes

A series of novel polynuclear mercury(II) diimine complexes with bridging chalcogenolate ligands have been synthesized and characterized and their luminescence and electrochemical properties studied. The crystal structures of [Hg(μ-SC6H4OCH3-p)(bpy)]n[PF6]n and [Hg(μ-SeC6H5)(bpy)]n[PF6]n have also been determined (bpy = 2,2′-bipyridine).

Electrogenerated chemiluminescence from Ru(ii) bipyridylphosphonic acid complexes adsorbed to mesoporous TiO2/ITO electrodes

Ru(II) diimine complexes having phosphonic acid substituents adsorb to TiO2 modified ITO electrodes and exhibit electrogenerated chemiluminescence when potentiostated at positive voltages in the presence of oxalate in buffered aqueous solutions.

Structural characterisation of new RuII[9]aneS3 polypyridylic complexes †

A large number of new [RuII([9]aneS3)(L)Cl]+ complexes (where L is a polypyridyl bidentate ligand) were synthesized from the precursor [Ru([9]aneS3)(dmso)Cl2] in the search for new DNA intercalators. The ancillary ligands used have different molecular architectures which include cross bridges, pyridyl units, phenanthroline and diamine derivatives. The related complex [Ru([9]aneS3)(ind)Cl2], containing the monodentate ligand indazole, was also prepared. The diimine complexes [Ru([9]aneS3)(pdi)Cl]+ and [Ru([9]aneS3)(phi)Cl]+ were prepared in situ from the ligands pda (o-phenylenediamine) and dap (phenanthrene-9,10-diamine), respectively, via Ru assisted amine/imine oxidation. All complexes were characterised through 1H NMR, IR, UV-Vis and electrospray mass spectrometry. Furthermore, the PF6 salts of seven [Ru([9]aneS3)(L)Cl]+ and [Ru([9]aneS3)(dip)Cl]BF4 (dip = 4,7-diphenylphenanthroline) have been investigated by X-ray single crystal diffraction. The crystal structures are presented and analysed in terms of the molecular assemblies of the complex cations and anions and the molecular hydrogen bonding interactions. The π-stacking geometric arrangements of the extended aromatic systems dppz (dipyrido[3,2-a∶2′,3′-c]phenazine) and dip in their metal complexes are also discussed.