Crystal structures of 7-azaindole, an unusual hydrogen-bonded tetramer, and of two of its methylmercury(II) complexes

Dufour, Pascal; Dartiguenave, Yves; Dartiguenave, Michèle; Dufour, N.; Lebuis, Anne‐Marie; Bélanger‐Gariépy, Francine; Beauchamp, André L.

doi:10.1139/v90-025

Cited by 47 publications

(44 citation statements)

References 12 publications

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“…Ligands 1 and 4 each form qne moderately strong (38) hydrogen bond (N...CI < 3.13 A) with a single chlorine. This corresporids to relatively small N(l 1)-N(17)-Cu(1)-Cl (1) and N(41)-N(47)-Cu(4)-Cl(4) torsion angles of 39.1(3) and 33.7(3)', respectively. For ligands 2 and 3, the torsion angles are close to 60°, so that the N-H bonds are roughly equidistant from two chlorines, with which they form bifurcated hydrogen bonds.…”

Section: C1(3)cu(l)c1(2)cu(2)c1(3) Chain Ismentioning

confidence: 89%

Preparation and structure of chloro-copper(II) complexes of 7-azaindole

Poitras¹,

Beauchamp²

1992

Can. J. Chem.

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The light green trans-CuCl2(Haza)2 adduct precipitates immediately from mixtures of CuCl2•2H2O with excess 7-azaindole (Haza) in methanol. Upon standing in azaindole-rich solution, this solid is replaced by a deep green Cu2Cl4(Haza)6 compound, whose crystal structure (orthorbombic, Fdd2, a = 26.558, b = 23.750, c = 12.727 Ǻ, Z = 8, R = 0.068, Rw = 0.066) shows the presence of square-planar [Cu(Haza)4]2+ and trans-[CuCl2(Haza)2] units connected by bridging Cl− ions, making each Cu atom (4 + 2)-coordinated. Azaindole is bonded to the metal via the pyridine N7 site, whereas the five-membered ring retains its N1—H proton. The azaindole ligands are disordered over two orientations in the [CuCl2(Haza)2] unit. The square-planar Cu species and apical Cl− ions lie on a twofold axis and define along c an infinite chain based on the [Formula: see text] pattern. Equimolar mixtures of azaindole and CuCl2•2H2O yield a brown Cu4OCl6(Haza)4 compound. The crystal structure of its ethyl acetate solvate (monoclinic, P21/c, a = 11.661, b = 22.415, c = 15.077 Ǻ, β = 109.85°, Z = 4, R = 0.048, Rw = 0.054) shows the presence of a tetranuclear cluster consisting of a μ4-oxide ion surrounded by a tetrahedron of Cu(II) atoms bridged in pairs by chlorine atoms. The trigonal-bipyramidal coordination of each copper atom is completed by a monodentate N7-bonded azaindole molecule hydrogen bonded to bridging chlorines via N1—H. The influence of complexation on the infrared spectrum of azaindole is discussed.

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Section: C1(3)cu(l)c1(2)cu(2)c1(3) Chain Ismentioning

confidence: 89%

Preparation and structure of chloro-copper(II) complexes of 7-azaindole

Poitras¹,

Beauchamp²

1992

Can. J. Chem.

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“…The validity of the computational methods used in this paper is provided by comparison of theoretical results with molecular structures and properties of the 7AI monomer that have been measured experimentally. The molecular geometries of 7AI monomer and dimer are both unknown, as the x-ray diffraction studies have revealed that 7AI forms a tetramer in the crystal state (18). Only the 7AI monomer rotational constants and the position of its pyrrole proton in the inertial axis frame are known in the gas phase (19).…”

Section: The Three Defining Simultaneity Principles Of Photo-induced mentioning

confidence: 99%

The concerted mechanism of photo-induced biprotonic transfer in 7-azaindole dimers: Structure, quantum-theoretical analysis, and simultaneity principles

Catalán

Pérez

Valle

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Six stable dimer models for 7-azaindole (including the classic C2h doubly hydrogen-bonded, coplanar, centrosymmetric dimer) are considered to be observable in adiabatic nozzle jet molecular beams. They are analyzed by hybrid density functional theory (DFT), the MP2 ab initio method for the ground electronic state, and the single-excitation configuration interaction (CIS) (over frozen ground state optimized geometries obtained from DFT) excited state calculations, for global potential minima and proton-transfer potential energy curves. Three simultaneity principles are stated: (i) intermolecular coherent excitation molecular exciton simultaneity, (ii) intramolecular acid-base change simultaneity at the pyrrolo-N-H and aza-N proton-donor, proton-acceptor sites, and (iii) intermolecular simultaneity of catalytic proton-donor, proton-acceptor action. It is suggested that the formation of the classic C2h dimer of 7-azaindole, which is considered exclusively by previous researchers, can be formed from at least one of the several card-pack hydrogen-bonded dimers in a secondary slower step approaching a microsecond scale, instead of the picosecond events at the supersonic nozzle. It is proposed that the complexity of dimerization modes is the basis of the postexcitation, postionization diverse kinetic isotope results.T he photoinduced biprotonic transfer in the classic 7-azaindole (7AI) hydrogen-bonded C 2h dimer (refs. 1 and 2 and references therein) seemingly has revealed contrasting mechanisms according to the experimental techniques applied. Electronic spectroscopic observations and quantum theoretical calculations require a concerted (3) one-step simultaneous intermolecular transfer of the two protons involved in the hydrogen bonding of the 7AI base pair. In contrast, femtosecond laser-pulsed photo-excitation followed by femtosecond laserpulsed ionization and then time-of-flight (TOF) mass spectrometry (4-6), or with giant laser pulse-induced coulomb explosion (7, 8) followed by TOF mass spectrometry of the resultant ions (and molecular fragments), has suggested to these researchers a two-step neutral H-atom transfer, based on kinetic analysis of the ion appearance and isotopic effects. We shall return to the question of neutral H-atom transfer vs. H ϩ (proton) transfer at the end of the companion paper (9).In the first part of this paper, we give an outline summary of the spectroscopic demands on simultaneity of the biprotonic transfer for the concerted transfer mechanism, and then in the second part we present an analysis of the structures and protontransfer potential functions and the energies of formation for the variety of 7AI stable dimers that could form at supersonic velocities in the adiabatic-nozzle supercooled molecular beam. This presentation is suggested as a pathway to resolving the conflict between the spectroscopic and the kinetic results. Background of 7AI Dimer Biprotonic TransferFor photo-induced biprotonic transfer we emphasize three strict requirements of simultaneity of action that must exist.

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“…(Table s-313, are not significantly different. N7-C6 coupling does not appreciably affect bond lengths and angles in the azaindolyl unit, but greater differences are found in the azaindolium ring (14). The bond lengths are increased by -0.02 A in the C(16)-N(17)-C(18)-C (19) region, whereas N(l1)-C (18) is shortened by the same amount.…”

Section: Reactants and Techniquesmentioning

confidence: 78%

“…The formally neutral 7-azaindole ligands is bonded via N7. The distances and angles in coordinated azaindole (Table 5) show no significant differences with those found in free azaindole and other complexes containing monodentate N7-bonded azaindole (14,16,(18)(19)(20). The ligand two-ring system is planar: the mean atom-to-plane distance (0.0!2 A) corresponds to l a with the largest deviation (0.023(10) A) found for N(7) (Table S-4)3.…”

Section: Reactants and Techniquesmentioning

confidence: 86%

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Reactions of 7-azaindole with niobium and tantalum pentachlorides and coupling to the azaindolyl-azaindolium cation

Poitras¹,

Beauchamp²

1994

Can. J. Chem.

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JACQUES POITRAS and AND& L. BEAUCHAMP. Can. J. Chem. 72, 1675Chem. 72, (1994. The reaction of NbC1, and TaC1, with 7-azaindole (Haza) at room temperature in benzene or dichloromethane yielded MCl,(Haza) addition compounds. Under more severe conditions, the same compound was obtained with TaCl,. For NbCl,, some reduction to Nb(IV) was observed and NbCI,(Haza), NbCI,(Haza),, and the (H,aza)' ion were identified in the reaction mixture by infrared spectroscopy. Oxidative coupling of two azaindole units via N7-C6 also took place during the reaction, since the 7-(azaindol-6-y1)azaindolium cation was found as counter-ion in the crystal structures of two complex salts. In the crystals of

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Crystal structures of 7-azaindole, an unusual hydrogen-bonded tetramer, and of two of its methylmercury(II) complexes

Cited by 47 publications

References 12 publications

Preparation and structure of chloro-copper(II) complexes of 7-azaindole

Preparation and structure of chloro-copper(II) complexes of 7-azaindole

The concerted mechanism of photo-induced biprotonic transfer in 7-azaindole dimers: Structure, quantum-theoretical analysis, and simultaneity principles

Reactions of 7-azaindole with niobium and tantalum pentachlorides and coupling to the azaindolyl-azaindolium cation

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