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Auxiliary Ligand (auxiliary + ligand)
Selected AbstractsTheoretical study on the influence of ancillary ligand on the spectroscopic properties and electronic structures of phosphorescent Pt(II) complexesINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2010Min Zhang Abstract The geometries, energies, and electronic properties of a series of phosphorescent Pt(II) complexes including FPt, CFPt, COFPt, and NFPt have been characterized within density functional theory DFT calculations which can reproduce and rationalize experimental results. The properties of excited-states of the Pt(II) complexes were characterized by configuration interaction with singles (CIS) method. The ground- and excited-state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. In addition, we also have performed a triplet UB3LYP optimization for complex FPt and compared it with CIS method in the emission properties. The datum (562.52 nm) of emission wavelength for complex FPt, which were computed based on the triplet UB3LYP optimization excited-state geometry, is not agreement with the experiment value (500 nm). The absorption and phosphorescence wavelengths were computed based on the optimized ground- and excited-state geometries, respectively, by the time-dependent density functional theory (TD-DFT) methods. The results revealed that the nature of the substituent at the phenylpyridine ligand can influence the distributions of HOMO and LUMO and their energies. Moreover, the auxiliary ligand pyridyltetrazole can make the molecular structure present a solid geometry. In addition, the charge transport quality has been estimated approximately by the predicted reorganization energy (,). Our result also indicates that the substitute groups and different auxiliary ligand not only change the nature of transition but also affect the rate and balance of charge transfer. By summarizing the results, we can conclude that the NFPt is good OLED materials with a solid geometry and a balanced charge transfer rate. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Comparison of collision- versus electron-induced dissociation of Pt(II) ternary complexes of histidine- and methionine-containing peptides,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2009Linda Feketeová Incubation of the histidine-containing peptides (GH, HG, GGH, GHG, HGG) and methionine-containing peptides (GM, MG, GGM, GMG, MGG) with the platinum complexes [Pt(terpy)Cl]+ (A) and [Pt(dien)Cl]+ (B) followed by electrospray ionisation (ESI) led to a number of singly and doubly charged ternary platinum peptide complexes, including [Pt(L)M]2+ and [Pt(L)M,H]+ (where L,=,the ligand terpy or dien; M is a peptide). Each of the [Pt(L)M]2+ complexes was subjected to electron capture dissociation (ECD), collision-induced dissociation (CID) and electron-induced dissociation (EID), while each of the [Pt(L)M,H]+ complexes was subjected to CID and EID. Results from ECD suggest that the free electron is captured by the metal ion thus weakening the bonds to its ligands. In the case of the ligand terpy, which binds more strongly than dien, this weakening leads to the loss of the peptide. The minor products in the ECD spectra of [Pt(terpy)M]2+ complexes do show fragmentation along the peptide backbone, but the ions observed are of the a-, b-, and y-type. For the complexes with methionine-containing peptides, a marker ion, [Pt(L)SCH3]+, was found which is indicative of binding of Pt to the methionine side chain. For the histidine-containing peptides, an ion containing platinum, the auxiliary ligand, and the histidine imine was observed in many instances, thus indicating the binding of the histidine side chain to the metal, but other modes of Pt coordination (N-terminus) were also found to be competitive. These findings are consistent with a recent finding (Sze et al. J. Biol. Inorg. Chem. 2009; 14: 163) that Pt occupies the methionine-rich copper(I)-binding site rather than histidine-rich copper(II)-binding site in the CopC protein. Copyright © 2009 John Wiley & Sons, Ltd. [source] Can radical cations of the constituents of nucleic acids be formed in the gas phase using ternary transition metal complexes?,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2005Sheena Wee Electrospray ionization (ESI) tandem mass spectrometry (MS/MS) of ternary transition metal complexes of [M(L3)(N)]2+ (where M,=,copper(II) or platinum(II); L3,=,diethylenetriamine (dien) or 2,2,:6,,2,-terpyridine (tpy); N,=,the nucleobases: adenine, guanine, thymine and cytosine; the nucleosides: 2,deoxyadenosine, 2,deoxyguanosine, 2,deoxythymine, 2,deoxycytidine; the nucleotides: 2,deoxyadenosine 5,-monophosphate, 2,deoxyguanosine 5,-monophosphate, 2,deoxythymine 5,-monophosphate, 2,deoxycytidine 5,-monophosphate) was examined as a means of forming radical cations of the constituents of nucleic acids in the gas phase. In general, sufficient quantities of the ternary complexes [M(L3)(N)]2+ could be formed for MS/MS studies by subjecting methanolic solutions of mixtures of a metal salt [M(L3)X2] (where M,=,Cu(II) or Pt(II); L3,=,dien or tpy; X,=,Cl or NO3) and N to ESI. The only exceptions were thymine and its derivatives, which failed to form sufficient abundances of [M(L3)(N)]2+ ions when: (a) M,=,Pt(II) and L3,=,dien or tpy; (b) M,=,Cu(II) and L3,=,dien. In some instances higher oligomeric complexes were formed; e.g., [Pt(tpy)(dG)n]2+ (n,=,1,13). Each of the ternary complexes [M(L3)(N)]2+ was mass-selected and then subjected to collision-induced dissociation (CID) in a quadrupole ion trap. The types of fragmentation reactions observed for these complexes depend on the nature of all three components (metal, auxiliary ligand and nucleic acid constituent) and can be classified into: (i) a redox reaction which results in the formation of the radical cation of the nucleic acid constituent, N+.; (ii) loss of the nucleic acid constituent in its protonated form; and (iii) fragmentation of the nucleic acid constituent. Only the copper complexes yielded radical cations of the nucleic acid constituent, with [Cu(tpy)(N)]2+ being the preferred complex due to suppression, in this case, of the loss of the nucleobase in its protonated form. The yields of the radical cations of the nucleobases from the copper complexes follow the order of their ionization potentials (IPs): G (lowest IP),>,A,>,C,>,T (highest IP). Sufficient yields of the radical cations of each of the nucleobases allowed their CID reactions (in MS3 experiments) to be compared to their even-electron counterparts. Copyright © 2005 John Wiley & Sons, Ltd. [source] Coordination Chemistry of Conformation-Flexible 1,2,3,4,5,6-Cyclohexanehexacarboxylate: Trapping Various Conformations in Metal,Organic FrameworksCHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2008Jing Wang Abstract To study the conformations of 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (H6L), eleven new coordination polymers have been isolated from hydrothermal reactions of different metal salts with 1e,2a,3e,4a,5e,6a -cyclohexanehexacarboxylic acid (3e+3a, H6LI) and characterized. They are [Cd12(,6 - LII)(,10 - LII)3(,-H2O)6(H2O)6],16.5,H2O (1), Na12[Cd6(,6 - LII)(,6 - LIII)3],27,H2O (2), [Cd3(,13 - LII)(,-H2O)] (3), [Cd3(,6 - LIII)(2,2,-bpy)3(H2O)3],2,H2O (4), [Cd4(,4 - LVI)2(4,4,-Hbpy)4(4,4,-bpy)2(H2O)4],9.5,H2O (5), [Cd2(,6 - LII)(4,4,-Hbpy)2(H2O)10],5,H2O (6), [Cd3(,11 - LVI)(H2O)3] (7), [M3(,9 - LII)(H2O)6] (M=Mn (8), Fe (9), and Ni (10)), and [Ni4(OH)2(,10 - LII)(4,4,-bpy)(H2O)4],6,H2O (11). Three new conformations of 1,2,3,4,5,6-cyclohexanehexacarboxylate, 6e (LII), 4e+2a (LIII) and 5e+1a (LVI), have been derived from the conformational conversions of LI and trapped in these complexes by controlling the conditions of the hydrothermal systems. Complexes 1 and 2 have three-dimensional (3D) coordination frameworks with nanoscale cages and are obtained at relatively low temperatures. A quarter of the LI ligands undergo a conformational transformation into LII while the others are transformed into LIII in the presence of NaOH in 2, while all of the LI are transformed into LII in the absence of NaOH in 1. Complex 3 has a 3D condensed coordination framework, which was obtained under similar reaction conditions as 1, but at a higher temperature. The addition of 2,2,-bipyridine (2,2,-bpy) or 4,4,-bipyridine (4,4,-bpy) to the hydrothermal system as an auxiliary ligand also induces the conformational transformation of H6LI. A new LVI conformation has been trapped in complexes 4,7 under different conditions. Complex 4 has a 3D microporous supramolecular network constructed from a 2D LIII -bridged coordination layer structure by ,-, interactions between the chelating 2,2,-bpy ligands. Complexes 5,7 have different frameworks with LII/LVI conformations, which were prepared by using different amounts of 4,4,-bpy under similar synthetic conditions. Both 5 and 7 are 3D coordination frameworks involving the LVI ligands, while 6 has a 3D microporous supramolecular network constructed from a 2D LII -bridged coordination layer structure by interlayer N4,4,-HbpyH,,,O(LII) hydrogen bonds. 3D coordination frameworks 8,11 have been obtained from the H6LI ligand and the paramagnetic metal ions MnII, FeII, and NiII, and their magnetic properties have been studied. Of particular interest to us is that two copper coordination polymers of the formulae [{CuII2(,4 - LII)(H2O)4}{CuI2(4,4,-bpy)2}] (12,,) and [CuII(Hbtc)(4,4,-bpy)(H2O)],3,H2O (H3btc=1,3,5-benzenetricarboxylic acid) (12,,) resulted from the same one-pot hydrothermal reaction of Cu(NO3)2, H6LI, 4,4,-bpy, and NaOH. The Hbtc2, ligand in 12,, was formed by the in situ decarboxylation of H6LI. The observed decarboxylation of the H6LI ligand to H3btc may serve as a helpful indicator in studying the conformational transformation mechanism between H6LI and LII,VI. Trapping various conformations in metal-organic structures may be helpful for the stabilization and separation of various conformations of the H6L ligand. [source] Phosphonylation of 2-Amino- and 2-Amido-3-bromopyridines and 2-Amino-3-chloroquinoxalines with Triethyl PhosphiteEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2009M. Shaker S. Adam Abstract The Tavs reaction of 2-amino- and 2-acylamido-3-bromopyridines 1 and 2 with triethyl phosphite in the presence of palladium acetate or chloride allows the synthesis of 2-amino- and 2-acylamidopyridine-3-phosphonates 3 and 4. A second ring nitrogen atom causes strong activation and leads to excellent yields in the phosphonylation of 2-amino-3-chloroquinoxalines. 2,3-Dichloroquinoxaline does not need a catalyst and undergoes double phosphonylation with sodium diethyl phosphite under Michaelis,Becker conditions. The results show an activating influence of pyridine nitrogen (,M) and deactivating influence of the amino group (+M). The reactivity of 1 and 2 in the Tavs coupling is compared with that of the 3-NH-2-bromopyridine position isomers and 2-bromoanilines and discussed in terms of the opposite effects of pyridine and amino(amido) nitrogen and different position of the N atoms towards the reaction site. The advantage of the Tavs reaction is the easy optimization because neither auxiliary ligands are required nor a base to trap the halide or a solvent. Triethyl phosphite itself acts as ligand and forms Pd0{P(OEt)3}n in the initial phase of the reaction. The structures of the products and the expected intramolecular N,H···O=P hydrogen bridging bonds were proven by solution NMR and by X-ray crystal structure analysis of single crystalline 3c.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] 15N NMR coordination shifts in Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with pyridine, 2,2,-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2,-biquinoline, 2,2,:6,, 2,-terpyridine and their alkyl or aryl derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2008Leszek Pazderski Abstract The 15N NMR data for 105 complexes of Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with simple azines such as pyridine, 2,2,-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2,-biquinoline, 2,2':6', 2"-terpyridine and their alkyl or aryl derivatives have been reviewed. The 15N NMR coordination shifts, i.e. the differences between the 15N chemical shifts of the same nitrogen in the molecules of the complex and the ligand (,15Ncoord = ,15Ncompl , ,15Nlig), have been related to some structural features of the reviewed coordination compounds, like the type of the central ion and the character of auxiliary ligands (mainly in trans position). These ,15Ncoord parameters are negative, their absolute magnitudes (ca 30,150 ppm) generally increasing in the metal order Au(III) < Pd(II) < Pt(II) and Rh(III) < Co(III) < Pt(IV) < Ir(III), as well as with the enhanced trans influence of the other donor atoms (H, C , Cl < N). Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||