Spectroscopic and electrochemical properties of dichlorodiimine complexes of Au(III) and Pt(II) with 1,4-diazine derivatives of o-phenanthroline

A series of dichlorodiimine complexes [M(N N)Cl₂]^z of Au(III) and Pt(II) with 1,4-derivatives of o-phenanthroline [(N N) = o-phenanthroline (phen), dipyrido[f,h]quinoxaline (dpq), dipyrido[a,c]phenazine (dppz), 6,7-dicyanodipyrido[f,h]quinoxaline (dicnq)] were prepared and characterized by ¹H NMR, electronic absorption, and emission spectroscopy and by cyclic voltammetry. In all the complexes, the ³(π-π*)-type transition is the spin-forbidden transition of the lowest energy, responsible for the luminescence. The longest wave bands in the absorption spectra of the Au(III) and Pd(II) complexes were assigned in accordance with the results of the electrochemical studies to the ¹(d*)-and ¹(d*)-type transitions, respectively.     

Luminescent cyclometalated iridium(III) dipyridoquinoxaline indole complexes as biological probes

Four luminescent cyclometalated iridium(III) dipyridoquinoxaline complexes appended with an indole moiety [Ir(N∧C)₂(N∧N)] (PF₆) (HN∧C = 2-phenylpyridine, Hppy; N∧N = 2-(N-(2-(indole-3-acetamido)ethyl)aminocarbonyl)dipyrido[3,2-f:2′,3′-h]quinoxaline, dpqC2indole (1a), N∧N = 2-(N-(6-(indole-3-acetamido)hexyl)aminocarbonyl)dipyrido[3,2-f:2′,3′-h]quinoxaline, dpqC6indole (1b); HN∧C = 7,8-benzoquinoline, Hbzq, N∧N = dpqC2indole (2a), N∧N = dpqC6indole (2b)) have been synthesized and characterized. Upon irradiation, all the complexes displayed moderately intense and long-lived luminescence under ambient conditions and in 77 K glass. On the basis of the photophysical data, the emission of the complexes has been assigned to an excited state of triplet metal-to-ligand charge-transfer (³MLCT) ((dπ(Ir) → π*(N∧N)) character. Cyclic voltammetric studies revealed indole-based and iridium-based oxidations at ca. +1.10 V and +1.24 V vs. SCE, respectively, and ligand-based reductions at ca. ?1.07 to ?2.29 V vs. SCE. The interactions of the complexes with an indole-binding protein, bovine serum albumin (BSA), have been examined by emission titrations.     

Spectroscopic and electrochemical properties of cyclopalladated complexes derived from 2,3-diphenylpyrazine

A comparative study of complexes [Pd(dphpz)(N∧N)]PF₆ [dphpz^? is the deprotonated form of 2,3-diphenylpyrazine; (N∧N) is ethylenediamine (En), 2,2′-bipyridine (bpy), o-phenanthroline (phen), dipyrido[a,c]phenazine (dppz), 6,7-dicyanopyrido[f,h]quinoxaline (dicnq)] was made, using ¹H NMR, electronic absorption, and emission spectroscopy, and also cyclic voltammetry. Steric interaction of the dphpz^? phenyl rings leads to significant proton shielding in the carbanionic moiety of the cyclometallated ligand. Introduction of heterocyclic diimines instead of ethylenediamine decreases the desheilding of the dphpz^? protons adjacent to the coordination center. Irrespective of the nature of the N∧N ligands, the cyclopalladated complexes are characterized by specific parameters of photo-and electrostimulated electron transfer processes involving the Pd(dphpz) orbitals, namely, by the long-wave absorption band with λ_max 395±6 nm and ε (2.2±1.2) × 10³ 1 mol^?1 cm^?1, the vibrationally structured low-temperature (77 K) luminescence resulting from the spinforbidden optical transfer from the excited to the ground state of the complex (energy E ⁰⁰ 19.27±0.07 kK, lifetime τ 160±30 μs), and the one-electron electroreduction wave with E ₁?(2.0±0.1)V. For the [Pd(dphpz)·(N∧N)]⁺ complexes containing diazine derivatives of phenanthroline (dppz, dicnq), the degradation of the photoexcitation energy from two electronically excited states can occur as isolated process with successive transfer of electrons to the π orbitals localized on the remote moieties: [Pd(dphpz)] and diazine fragments of the N∧N ligands.     

Intensités des transitions optiques de [PtCl4]2−

The oscillator strengths of the “d-d” transitions of the ion [PtCl₄]^2? were calculated. The method, based on the evaluation of the MO of the distorted ion, gives results in good accordance with the experimental data. The transition to ¹ B _1g (a _1g →b _1g ^* ), as a consequence of the participation of the orbital 6s, mixed with \(5d_{z^2 } \) in \(a_{1_g } ,a_{1_g } \) is characterized by a very low intensity in the case of thex,y polarization.     

Dichlorotriethylphosphine-[N-formyl-N,N′-bis(3,4-dimethoxy)benzyl-trimethylenediamine] platinum(II)

By treatment of 1,3-bis(3,4-dimethoxybenzyl)-3,4,5,6-tetrahydropyrimidinium chloride (1) with KOBu ^t and [PtCl₂(PEt₃)₂]₂ N-coordinated platinum complex (2) is obtained. The Pt atom is coordinated in square planar arrangements by two chloride ions in a trans-configuration, the N-formyl-N,N′-bisaryltrimethylenediamine nitrogen atom, and the phosphine P atom. An extensive three-dimensional network of three C-H…O hydrogen bonds, two C-H…π and one π…π interactions are responsible for the crystal stabilization. Intermolecular hydrogen bonds and C-H…π interactions produce R ₂ ² (6), R ₂ ² (22), R ₂ ² (24), R ₃ ³ (23), R ₄ ⁴ (26), and R ₄ ⁴ (32) rings.     

Spectroscopic properties of the Ar 2 * (5p) excimer states

The transitions between Ar ₂ ^* (5p) and Ar ₂ ^* (4sΣ _u) have been investigated by absorption spectrometry. The fine structure of the Ar ₂ ^* (5p ³ Π _g) was attributed to a predominantly Hund’s case a coupling. A spin orbit coupling constant of A = (9.8±0.3) cm^-1 results. Absorption by the singlet system allows one to determine the triplet/singlet splitting between the Ar ₂ ^* (4s Σ _u) states to be (540 ± 100) cm^-1. The transition probabilities of the Ar ₂ ^* (5p) and Ar ₂ ^* (6p) levels were determined by saturation spectrometry yielding values between (0.2–2.5) · 10⁶ s^-1.     

Isomerization of linear C3H 3 + in its reaction with acetylene,and collisional stabilization of the [C5H 5 + ]* collision complex in a quadrupole ion trap mass spectrometer

The isomerization of linear C₃H ₃ ⁺ in its reaction with acetylene to cyclic C₃H ₃ ⁺ was studied with a quadrupole ion trap mass spectrometer. The reaction of linear C₃H ₃ ⁺ with ¹³C₂H₂ shows that isomerization takes place via a [C₅H ₅ ⁺ ]^* activated complex that is unstable relative to disproportionation back into the cyclic and linear forms of C₃H ₃ ⁺ and acetylene. The formation of carbon-13 labeled cyclic and linear C,Hi indicates that isomerization involves skeletal exchange. Collisional stabilization of the [C₅H ₅ ⁺ ]^* collision complex was achieved at a helium pressure of approximately 1 mtorr.     

A group theoretical paradigm for describing the skeletal molecular orbitals of cluster compounds. Part 3

The group theoretical consequences of the Tensor Surface Harmonic Theory have been developed for [ML₂] _n , [ML₄] _n and [ML₅] _n clusters where either thexz andyz orx ²?y ² andxy components toL _d ^π andL _d ^δ do not contribute equally to the bonding. The closed shell requirements for such clusters are defined and the orbital symmetry constraints pertaining to the interconversion of conformers of these clusters are described.     

Synthesis of bismuth complexes from bismuth iodide and ammonium and phosphonium salts

The complexes [Et₂NH₂] ₃ ⁺ [BiCl₆]^3? (I), [NH₄]⁺[BiI₄(C₅H₅N)₂]^?·2C₅H₅N (II), [Ph₃MeP] ₂ ⁺ [BiI₅]^2? (III), [Ph₃MeP] ₂ ⁺ [BiI₅(C₅H₅N)]^2?·C₅H₅N (IV), [Ph₃MeP] ₃ ⁺ [Bi₃I₁₂]^3? (V), [Ph₃(i-Pr)P] ₃ ⁺ [Bi₃I₁₂]^3?·2Me₂C=O (VI), [Ph₃BuP] ₂ ⁺ [Bi₂I₈·₂Me₂C=O]^2? (VII), and [Ph₃BuP] ₂ ⁺ [Bi₂I₈·2Me₂S=O]^2? (VIII) were obtained by reactions of bismuth iodide with ammonium and phosphonium iodides in acetone, pyridine, or dimethyl sulfoxide.     

Niobium-chloride octahedral clusters as building units for larger frameworks

A systematic theoretic study on clusters containing edge-bridged octahedral metal units [Nb₆Cl₁₂] ⁿ (n?=?2, 3, or 4) and a large variety of ligands has been performed. The benchmark results on the [Nb₆Cl ₁₂ ⁱ ] ⁿ⁺ and [Nb₆Cl ₁₂ ⁱ Cl ₆ ^a ] ⁿ (n?=?2, 3 or 4) cluster units demonstrated the reliability of GGA PBE functional in combination with ZORA TZP basis set for the Nb-containing coordination compounds. The geometrical, electronic, and vibrational properties of large variety of substituted Nb₆Cl ₁₂ ⁱ Y ₆ ^a clusters have been provided. One- and two-dimensional structures with a [Nb₆Cl ₁₂ ⁱ (Bipyr) _x Cl _6?x ^a ] (x?=?2 and 4) building blocks have been proposed as good and stable candidates for new coordination polydimensional materials.     

The nature of molecular oxygen binding and activation in Mn-O2 complex

Non-empirical calculations of CASSCF energies, electric dipole moments, Einstein coefficients, matrix elements of the operator of spin-orbital interaction between states of different multiplicity in a model complex ^6,8[Mn-O₂] of C _2v symmetry have been made in 3-21G, 6-31G, 6-31G** basis sets. The crosssections of the potential energy surface (PES) of the ground and excited states were built. It is found that oxygen bonding to manganese is possible when excited atoms of manganese collide with molecular oxygen, singlet oxygen with Mn[⁶ S _5/2] atoms, or in a close contact O₂[X³Σ _g ^? ] + Mn[⁶ S _5/2] and is determined by charge transfer states ^6,8CTS(Mn⁺O ₂ ^? ). Mechanisms of singlet oxygen activation/deactivation are determined by a considerably increased probability of electric dipole transitions b ¹Σ _g ⁺ ?a ¹Δ_g, a ¹Δ_g?X³Σ _g ^? , b ¹Σ _g ⁺ ?X³Σ _g ^? induced in oxygen in the collision process.     

Complexes of Cu(II) and Co(II) nitrates with 3-Phenyl-5,5-dimethyl-5,6-dihydro-1,2,4-triazolo[3,4-a]isoquinoline

Complexes of Cu(II) and Co(II) nitrates with 3-phenyl-5,5-dimethyl-5,6-dihydro-1,2,4-triazolo[3,4-a]isoquinoline (L⁰) of the composition [CuL ₂ ⁰ (NO₃)₂] (I) and [CoL ₂ ⁰ (NO₃)₂] · CH₃CN (II) are synthesized and their crystal structures are determined by X-ray diffraction. The L⁰ ligand is coordinated to the metal atoms through the N atom in position 2 of triazole fragment. The coordination polyhedron of the Cu(II) atom is a square with two additional axial vertices, while that of the Co(II) atom is a tetrahedron with two additional vertices. The NO ₃ ^? groups in the structures of I and II perform similar anisobidentate function. Complexes I and II are studied by IR and electronic spectroscopy.     

Carbon-free D3d [E3ME3]2− (E=P, As; M=Ni, Pd, Pt): The smallest inorganic sandwich complexes with aromatic η3-P 3 − and η3-As 3 − ligands

A density functional theory and wave function theory investigation on the possibility of carbon-free phosphametallocenes [P₃MP₃]^2? and arsenametallocenes [As₃MAs₃]^2? (M=Ni, Pd, Pt) is presented in this work. Staggered singlet D_3d [E₃ME₃]^2? (E=P, As)-the smallest inorganic metallocenes possible to construct-proved to be the global minima of the heptaatomic systems and may be targeted in future experiments. Cyclo-P ₃ ^? and cyclo-As ₃ ^? turned out to possess similar aromaticity to cyclo-P ₅ ^? and cyclo-As ₅ ^? and may serve as effective ligands to sandwich a wide range of transition metals. The first vertical electron detachment energies of C_s [E₃ME₃]Li^? monoanions with a staggered [E₃ME₃]^2? sandwich core were predicted to be between 2.7 and 2.9 eV; the extent of stabilization by Li⁺ suggests that such materials be viable targets for experimental characterization.     

The interaction of metastable helium atoms with alkali atoms

Using crossed beams of ground state alkali atoms A (A = Li, Na, K, Rb, Cs) and metastable He(2³ S), He(2¹ S) atoms, we have measured the energy spectra of electrons resulting in the respective Penning ionization processes at: thermal collision energies. The data are interpreted to yield the well depthD _e ^* of the²Σ interaction potentials as follows: He(2³ S)+A:D _e ^* (A=Li)=868(20) meV;D _e ^* (Na)=740(25) meV;D _e ^* (K)=591(24) meV;D _e ^* (Rb)=546(18) meV;D _e ^* (Cs)=533(18) meV. He(2¹ S)+A:D _e ^* (Li)=330(17) meV;D _e ^* (Na)=277(24) meV;D _e ^* (K)=202(23) meV;D _e ^* (Rb)=219(18) meV;D _e ^* (Cs)=277(18) meV. The well depth for He(2³ S)+A(²Σ) is always close to 80% of the well depth for Li(2s)+A(X ¹Σ). The ionization cross sections for He(2¹ S)+A are about 3 to 4 times larger than those for He(2³ S)+A.     

Periodate ion as an oxidant in indicator reactions with aromatic amines

The kinetics of 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation by sodium periodate in an aqueous solution was studied. For the auto-acceleration regime, the experimental data correspond to the kinetic equation w _t = k[P] _t ^1/2 [IO ₄ ^? ] _t ^1/2 [TMB]₀, where w _t is the accumulation rate of the meriquinoid product (P) of TMB oxidation and [P]_t and [IO ₄ ^? ]_t are the concentrations of product P and periodate, respectively, at time t. A radical chain mechanism was proposed; the mechanism explains the experimental kinetic equation and complies with the observed inhibiting effect of metal ions (Zn, Cd) in this reaction.     

Lifetime measurements of the 2p 3d 3 D 1, 2, 3 0 and 2p 3d 1 P 1 0 levels in NII by beam-foil-laser spectroscopy

Accurate lifetimes measured by means of the cascade-free method based on laser excitation of a fast ion beam preexcited in a carbon foil are reported for four 2p 3d levels in NII. The lifetime results are: τ(2p 3d ³ D ₁ ⁰ )=0.209±0.007 ns, τ(2p 3d ³ D ₂ ⁰ )=0.219±0.007 ns, τ(2p 3d ³ D ₃ ⁰ )=0.217±0.005 ns, and τ(2p 3d ¹ P ₁ ⁰ )=0.410±0.017 ns. These results are compared to theoretical and experimental lifetimes reported previously.     

Electrochemical control of association and deposition of tetraviologen calix[4]resorcin

The association and deposition of tetraviologen calix[4]resorcin MVCA-C ₅ ⁸⁺ can be controlled using the electrochemical reduction-reoxidation cycle of viologen units. The monomeric MVCA-C ₅ ⁸⁺ was converted into the highly molecular (MVCA-C ₅ ^4+· ) _n associate (π-polymer) by reducing it to the MVCA-C ₅ ^4+· tetra(radical cation) and completely returns to the starting monomeric state by reverse oxidation. The reduction to the neutral state MVCA-C ₅ ⁰ allowed calixresorcin to pass from solution to precipitate and the reverse oxidation led to its returning in solution.     

Experimental and theoretical study of the hyperfine structure in the (5d+6s)96p configurations of Pt I

The hyperfine structure of the odd configurations 5d ⁹6p and 5d ⁸6s6p was studied with laser optogalvanic spectroscopy and high resolution interferometry in a platinum hollow cathode. A parametric hyperfine structure analysis for the configurations (5d+6s)⁹6p with 10 excited odd-parity levels was performed for¹⁹⁵Pt. We obtained one-electron hfs parameters,a _5d ⁰¹ =1160(320) MHz,a _6s ¹⁰ =35600(5300) MHz anda _6p ⁰¹ =1300(780) MHz for the configuration 5d ⁸6s6p. The corresponding $\left\langle {r^{ - 3} } \right\rangle _{nl}^{k_s k_l } $ values are compared with those known for other 5d-elements.     

Guided ion beam studies of the reactions of O+, O 2 + , N+ and N 2 + with silane

Guided ion beam mass spectrometry is used to measure the cross sections as a function of kinetic energy for reaction of SiH₄ with O⁺(⁴S), O ₂ ⁺ (²Π_g,v=0), N⁺(³P), and N ₂ ⁺ (²Σ _g ⁺ ,v=0). All four ions react with silane by dissociative charge-transfer to form SiH _m ⁺ (m=0?3), and all but N ₂ ⁺ also form SiXH _m ⁺ products where (m=0?3) andX=O, O₂ or N. The overall reactivity of the O⁺, O ₂ ⁺ , and N⁺ systems show little dependence on kinetic energy, but for the case of N ₂ ⁺ , the reaction probability and product distribution relies heavily on the kinetic energy of the system. The present results are compared with those previously reported for reactions of the rare gas ions with silane [13] and are discussed in terms of vertical ionization from the 1t ₂ and 3a ₁ bands of SiH₄. Thermal reaction rates are also provided and dicussed.