The Radical Anions of [2.2.2.2]Paracyclophane-1,9,17,25-tetraene and Some of its Heteroaromatic Analogues

The radical anions of [2.2.2.2]paracyclophane- 1,9,17,25-tetraene (I), [2] (2, 5)-furano [2]paracyclo [2] (2,5)furano [2]paracyclophane-1,8, 16,23-tetraene (II), [2]-(2,5)thiopheno [2]paracyclo [2] (2,5)thiopheno [2]paracyclophane-1,8,16,23-tetraene (III) and [2.2.2.2](2,5)thiophenophane-1,8,15,22-tetraene (IV) have been studied by ESR. and ENDOR. spectroscopy. The assignment of the proton coupling constants, a_Hμ is to a large extent based on investigations of deuteriated derivatives. These investigations impressively demonstrate the potential of ENDOR. spectroscopy as an analytical tool. The Arrhenius activation energies, E_a, for the rotation of phenylene fragments about the bonds linking them with the ethylenic parts in I ? and II ? are 36±6 and 28±4 kJ/mol, respectively. The value a_Hμ of the olefinic protons in I? appears substantially smaller than expected for the corresponding planar radical anion. The hyperfine data for II ?, III ? and IV ? are consistent with the conformations which should minimize the deviations of the macrocyclic π-systems from planarity. In the case of II ?, tight ion pairs are formed by the radical anion and its counter-ion, K ⊕, in DME , owing to the strong association of the alkali metal cation with one of the furan moieties. An analogous interaction of K ⊕ with a thiophene moiety in III ? must be weaker, since no effects of ion pairing on the ESR. and ENDOR. spectra have been observed for this radical anion.     

The Radical Anion of 2,7-Diazapyrene,a Change in Orbital Sequence on Protonation

ESR.-spectra are reported for the radical anion I · Θ of 2,7-diazapyrene (I), along with those for the radical cations I(2H) · ⊕ and I(2 CH₃) · ⊕ of 2,7-dihydro-2,7-diazapyrene and its 2,7-dimethyl-derivative, respectively. In contrast to the analogous radical ions of 4,4′-bipyridyl (II) and other previously studied diazaaromatic compounds, there is a striking change in the ¹⁴N and proton coupling constants on going from the radical anion I · Θ to the radical cations I(2H) · ⊕ and I(2 CH₃) · ⊕. This change can be rationalized in terms of the HMO model of the pyrene π-system. A reversal in the energy sequence of the lowest antibonding orbitals is predicted upon an increase in the absolute value of the Coulomb integral for the azasubstituted π-centres, such an increase simulating the enhanced electronegativity of the azanitrogen atoms 2 and 7 on protonation.     

ESR.-Studies of Nonalternant Radicals Structurally Related to Phenalenyl

The radical anion and the radical cation of azuleno[1,2,3-cd]phenalene (III) have been investigated by ESR. spectroscopy, along with the radical anion of 2-phenylazulene (IV). Also studied has been the neutral radical obtained by one-electron reduction of cyclohepta[cd]phenalenium-cation (VI^⊕). Assignment of the proton coupling constants for the radical ions III. ·?, III ·⊕ and IV·⊕, and the radical VI · is supported by comparison with the ESR. spectra of specifically deuteriated derivatives III-d₅ ·?, III-d₅ ·⊕, IV-d₂ ·? and VI-d₁′. The experimental results are in full accord with qualitative topological arguments and predictions of HMO models. Whereas the radical anion III ·? exhibits α-spin distribution similar to that of IV ·?the corresponding radical cation III ·⊕ and the neutral radical VI · are related in this respect to phenalenyl (V·). It is noteworthy that oxidation of III by conc. H₂SO₄ yields a paramagnetic species (IIIa ·⊕) which has a similar – but not an identical – structure as the radical cation III ·⊕ produced from III with AlCl₃ in CH₃NO₂.     

Radical Ions in the Pentalene Series [1]. Part II. Dibenzo [b,f]pentalene and its 5, 10-dimethyl derivative

Proton hyperfine data have been determined for the radical anions and cations of dibenzo [b,f]pentalene (III) and its 5, 10-dimethyl derivative (IV) . The assignment of the coupling constants to pairs of equivalent protons follows from a simple MO model, the use of which enables one to reproduce satisfactorily the experimental values. The proton hyperfine data, a_Hμ

1 The meaning of ^aH_μis ^aH? C(x),H? C(y),whereas only x and y are given in the particular cases.

, for the radical anion III?. correlate fairly well with the π-charge populations ?_μ derived from ¹H-NMR. spectra for the carbon centres μ in the dianion III^2?. The analogous correlation is less good in the case of the radical cation III⊕. and the dication III^2⊕., presumably due to the rough approximations involved in the evaluation of the numbers ?_μ for the latter species. The coupling constants a_H5,10 for III?. and III⊕. are very close to the corresponding values a_H4,6 for the radical ions of 1,3,5-tri-t-butylpentalene (II), in accord with the prediction of the MO model. A similarity is also found between the proton hyperfine data for III?. and those for the radical anions of structurally related 1,4-diphenyl-1,3-butadiene (V). On the other hand, there are striking changes in the coupling constants of the analogous protons on passing from III?. to the radical anions of dibenzo [a,e] cyclooctene (VI) and [16] annulene (VII), as a consequence of raising the symmetry from C_2h to D_2h and D_4h, respectively.     

π-Spin distribution in the radical anion of benzo[2.2]paracyclophane and its relation to those in the radical anions of [2.2](1,4)naphthalenophanes

Radical anions of benzo[2.2]paracyclophane (V) and its 1,2,12,12,14,15,17,18-octadeuterio derivative (V-d₈) in three ethereal solvents (DME, THF and MTHF) and in the temperature range of ?90 to ?50° have been studied by ESR. and ENDOR. spectroscopy. The resulting hyperfine data provide a detailed picture of the π-spin distribution in V · ? which is in full accord with expectation. In particular, it is noteworthy that the naphthalene moiety accommodates almost the entire π-spin population, as may be anticipated by the higher electron affinity of this π-system relative to benzene. The proton coupling constants for V · ? have been compared with those values for the radical anions of anti- and syn-[2.2](1,4)-naphthalenophanes (II and III, respectively) which were obtained under conditions of low frequency electron transfer between the two equivalent naphthalene moieties. Such a comparison corroborates the interpretation of the results reported previously for II · ? and III · ?.     

Two cadmium(II) addition compounds with 3-hydroxy-2,7-naphthalenedisulfonate containing aromatic diamines and their 3-D net

{[CdCl(2,2′-bipy)₂(H₂O)]⁺·[Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?·3H₂O} (1) and {[Cd(phen)₃]²⁺·2[Cd(3-O^?-2,7-NDS)(phen)₂]^?·8.5H₂O} (2) (3-OH-2,7-NDS?=?3-hydroxy-2,7-naphthalenedisulfonate, phen?=?1,10-phenanthroline, and 2,2′-bipy?=?2,2′-bipydine) were prepared and characterized by X-ray single-crystal diffraction. Compound 1 contains a discrete coordination cation [CdCl(2,2′-bipy)₂(H₂O)]⁺ and a coordination anion [Cd(3-O^?-2,7-NDS)(2,2′-bipy)₂]^?; 2 contains a discrete coordination cation [Cd(phen)₃]²⁺ and two coordination anions [Cd(3-O^?-2,7-NDS)(phen)₂]^?. There are numerous weak interactions among the coordination cation, coordination anion, and free water molecules, such as O–H?···?O hydrogen bonds, π?···?π stacking, and Cl^??···?π interactions in 1 and π?···?π stacking and C–H?···?π interactions in 2. The cations and anions as building blocks are connected to construct different 3-D supramolecular architectures via weak intermolecular interactions. Particularly, the capsule structure of 1 was observed.     

Conformation of cationic N,N‐di­methyl­glycine in di­methyl­glycinium tri­fluoro­acetate

In the title compound, C₄H₁₀NO₂⁺·C₂F₃O₂^?, the main N—C—COOH skeleton of the protonated amino acid is nearly planar. The C=O/C—N and C=O/O—H bonds are syn and the two methyl groups are gauche to the methyl­ene H atoms. The conformation of the cation in the crystal is compared to that given by ab initio calculations (Hartree–Fock, self‐consistent field molecular‐orbital theory). The tri­fluoro­acetate anion has the typical staggered conformation with usual bond distances and angles. The cation and anion form dimers through a strong O—H?O hydrogen bond which are further interconnected in infinite zigzag chains running parallel to the a axis by N—H?O bonds. Weaker C—H?O interactions involving the methyl groups and the carboxy O atoms of the cation occur between the chains.     

Ionic species in irradiated poly(methyl methacrylate). A pulse radiolysis and ESR study

Poly(methyl methacrylate) free of initiators was synthesized by γ-irradiation and cast into transparent films. The samples were investigated by ns pulse radiolysis at various temperatures, and by ESR spectroscopy after γ irradiation at 77°K. Short-lived transients with optical absorptions at 440 and 725 nm were observed. The 440 nm absorption has been ascribed to the cation and the 725 nm absorption (εG = 3000 M^?1 cm^?1 (100 eV)^?1, τ_1/2 = 190 ns at ?13°C, E_a = 6.5 kcal/mol) to the anion. These assignments are based on ESR data of samples of poly(methyl methacrylate) and pivalic acid methyl ester deuterated at the ester deuterated at the ester and α-methyl groups, respectively, and subjected to thermal annealing and photobleaching. The anion decomposes on photobleaching by loss of the ester ·CH₃ radical, and the cation is proposed to decay by loss of the ·CH₃ radical from the α-methyl group. The thermal decay of the anion is discussed.     

Manifestations of noncovalent interactions in the solid state. Dimeric and polymeric self-assembly in imidazolium salts via face-to-face cation—cation π-stacking

Abstract

X-ray crystallographic investigation of the tertiary structure of simple 1-methylimidazolium (1-Meim) salts reveals that cation—cation face-to-face π—stacking with interplanar separations in the range typically seen for molecule—molecule and molecule—cation interactions are possible. Two salts are reported. 1-Meim-CF₃SO₃, 1, exists as a centrosymmetric dimer with an interplanar separation of only 3.16 Å. The two imidazolium rings are slipped to the extent that the interaction can be regarded as a manifestation of C—H…C—H dipole interactions. 1-Meim-NO₃ exists as a one-dimensional (1-D) polymer with interplanar separations of 3.65 Å. The cations are not as severely slipped as for 1 and the interactions can be regarded as the result of cation—cation and anion—anion complementary electrostatics. Semi-empirical calculations are used to rationalize the π-π stacking in both 1 and 2. Crystal data: 1-Meim-CF₃SO₃, 1, triclinic, P1, a=6.416(3) Å, b=7.617(4) Å, c=9.569(4) Å, α=85.36(4)°, β=86.08(3)°, γ=85.18(4)°, V=463.6(4) Å,³ Z=2, D_c =1.66 g cm^?3, μ=3.7 cm^?1, T=17°C, R=0.054 and R _w=0.076 for 1241 reflections; 1-Meim-NO₃, 2, monoclinic, P2₁/c, a=9.009(7) Å, b=9.988(6) Å, c=7.308(5) Å, β=94.93(6)°, V=655.2(8) Å,³ Z=4, D_c =1.47 g cm^?3, μ=1.2 cm^?1, T=17°C, R=0.060 and R _w=0.068 for 483 reflections.     

Wechselwirkungen in Kristallen. 106. Mitteilung. Die Klaviatur der Na⊕-Koordinationszahlen in ihren Carbazolanion-Salzen

Interaction in Crystals: The Keyboard of Na⊕ Coordination Numbers in Its Carbazole Anion Salts Some local minima in the shallow potential of the system carbazole anion, sodium cation, and the ethers tetrahydrofuran, 1,2-dimethoxyethane, diglyme, triglyme, tetraglyme, 15-crown-5 as well as 2.2.1-cryptand are explored experimentally and by quantum-chemical calculations. Three prototype contact-ion multiples of Na⊕-solvated carbazole anion M? salts have been crystallized and structurally characterized: polyether-solvated monomers [M?Na⊕_solv]₁, solvent-shared dimers [M?Na⊕_solv]₂, and solvent-separated polyions [(M?)nNa?_solv](^n?1)? [Na⊕_solv](n_?1). The Na⊕ coordination numbers stretch from 3 to 7 as illustrated by the compounds [(M?)₃Na+]??[Na+(2.2.1-crytand)]₂ for 3 and 7, [(M?)₂Na+(THF)₂]? [Na⊕(2.2.1-cryptand)] for 4 and 7, [M? Na+(diglyme)]₂ for 5, or [M? Na+(l 5-crown-5)] for 6. Structural comparison is based on literature analogies as well as on results of MNDO calculations concerning charge distribution and enthalpies of formation. Taken together, the results demonstrate the delicate energy balance, by which cation solvation can influence the formation of organic salts.     

Luminescent triply-bridged dicopper(I) complex possessing 3,5-bis{6-(2,2′-dipyridyl)}pyrazole as a bis-chelating ligand

A new triply-bridged dicopper(I) complex, [Cu₂(μ-dppm)₂(μ-HL)](NO₃)₂ (1), has been prepared via successive treatment of cupric nitrate trihydrate with bis(diphenylphosphino)methane (dppm) and 3,5-bis{6-(2,2′-dipyridyl)}pyrazole (HL) in 2?:?4?:?1 molar ratio in dichloromethane. X-ray diffraction analysis of 1 reveals that the two Cu(I)s are in highly distorted tetrahedral environments with a distance of 4.2775(10)?Å, triply bridged by two dppm ligands and one HL chelate as a bis-bidentate bridging ligand through two bipyridyl moieties. Intermolecular N···H–C hydrogen bonding and π···H–C interactions assemble the [Cu₂(μ-dppm)₂(μ-HL)]²⁺ cations into a 3-D supramolecular architecture with extended channels along the b-axis, filled with methanol and anions. Complex 1 shows weak low-energy absorptions at 350–425?nm, tentatively ascribed to Cu(I) to HL metal-to-ligand charge-transfer (MLCT) transition, probably mixed with some ILCT character inside HL. The emission is observed at ambient temperature for 1, both in solution and in the solid state, originating from the MLCT excited states.     

Secondary interactions in 4‐bromo‐N,N‐dimethylanilinium bromide

The crystal packing of the title compound, C₈H₁₁BrN⁺·Br^?, involves three types of secondary interaction: a classical N—H?Br^? hydrogen bond, a `weak' but short C—H?Br^? interaction (normalized H?Br distance of 2.66 Å) and a cation–anion Br?Br contact of 3.6331 (4) Å. The hydrogen bonds connect two cations and two anions to form rings of graph set R(14). The Br?Br contacts link these rings to form layers parallel to the bc plane.     

Crystal Structure of [Co2(μ-dmg)2(μ-dmg H)(dmg H)(Pø3)] 1/2 dmg H2 · 1/2 CH3OH: A Crystal Containing Various Forms of dmg Ligand

The crystal structure of [Co₂(μ-dmg)₂(μ-dmg H)(dmg H)(Pø₃)] · 1/2 dmg H₂ · 1/2 CH₃OH has been determined by single crystal X-ray diffraction. The title complex crystallizes in triclinic space group P&1bar; with a=10.859(3), b=13.299(3), c=15.247(3)Å, α=98.52(2), β=99.26(2), γ=97.80(2)° and Z=2. The agreement indices are R(F)=0.062 and R_w(F)=0.085 for 5231 observations and 515 variables. Both cobalt atoms have an oxidation state of 3+ and are both six-coordinated; one Co(III) atom is bonded to a phosphorous atom of triphenylphosphine, four nitrogen atoms of two planar ligands, dmg^2? and dmgH^?, and one oxygen atom of another dmg^2? ligand. The other Co(III) atom is coordinated by four nitrogen atoms of two cis nonplanar ligands, dmg^2?, dmgH^?, and two oxygen atoms of the other dmg^2? and dmgH^? ligands. There are three N-O bridged ligands namely two dmg^2? and one dmgH^? between two Co(III) atoms. A free molecule of dmgH₂ and a molecule of CH₃OH are also found in the crystal lattice. The structure interestingly demonstrates the possible various forms of dmg, not only on their charge but also in different conformations upon coordination.     

A tetradentate bisoxime and its supramolecular nickel(II) cluster: synthesis,crystal structure,and spectral properties

Salen-type bisoxime 5,5′-dimethoxy-2,2′-[(ethylenedioxy)bis(nitrilomethylidyne)]diphenol (H₂L) and its trinuclear Ni(II) cluster {[(NiL)(n-BuOH)]₂(μ-OAc)₂Ni}?·?n-BuOH have been synthesized and structurally characterized. The structure of H₂L adopts an L-shape conformation where the two salicylaldoxime moieties are well separated. In the trinuclear Ni(II) cluster, two acetates coordinate to three Ni(II)'s through Ni–O–C–O–Ni bridges, four μ-phenoxos from two [NiL(n-BuOH)] units also coordinate to Ni(II), and two n-butanols coordinate to two terminal Ni(II)'s forming a distorted octahedral geometry. The Ni–O–C–O–Ni and μ-phenoxo bridges play important roles in assembling Ni(II) and the ligands. H₂L forms a rectangle-like large cave structure through O–H?···?N, C–H?···?O, and C–H?···?π hydrogen-bond interactions, whereas its trinuclear Ni(II) cluster exhibits a 3-D supramolecular network structure through intermolecular O–H?···?O, C–H?···?O, and C–H?···?π hydrogen-bond interactions.     

Einelektronen-Redox-Reaktionen von Octaphenyl[4]radialen: Erzeugung und ESR/ENDOR-Charakterisierung seines Radikal-Anions und Radikal-Kations

One-Electron Redox Reactions of Octaphenyl[4]radialene: Generation and ESR/ENDOR Characterisation of Its Radical Anion and Radical Cation The cyclovoltammograms of octaphenyl[4]radialene in DMF or THF at room temperature disclose each two quasireversible reduction and oxidation potentials at ?1.4 V/?1.7 V and +0.7 V/+0.9 V. Accordingly, both the radical anion and the radical cation can be generated: Ph₈C by K metal mirror reduction of a [2.2.2]cryptand containing THF solution, and Ph₈C by TI^3⊕(^?OOCCF₃)₃ oxidation in H₂CCl₂. Their ESR/ENDOR and General Triple spectra differ considerably in the number of resolved ¹H couplings (M^·?: 5 and M^·⊕: 3) as well as in their spectral widths (M^·?: a_1H 0.090 to 0.017 mT; M^·⊕: a_1H 0.066 to 0.023 mT) suggesting different changes in the D_2d structure of the neutral molecule on electron uptake or extrusion.     

Dimeric Radical Cation of 4,5,7,8-Tetramethyl[2.2]paracyclophane

Electrolytic oxidation of 4,5,7,8-tetramethyl[2.2]paracyclophane (I) yields a paramagnetic species which by ESR. spectroscopic evidence must be ascribed to the dimeric radical cation I₂ · ⊕. Analogous dimers are obtained from the 12, 13, 15, 16-tetradeuterio- and 1, 1, 10, 10, 12, 13, 15, 16-octadeuterio-derivatives of I so that all coupling constants can be unequivocally assigned to sets of equivalent protons. The hyperfine data for I₂ · ⊕ are consistent with an effective D_2h or D_2d symmetry, the four benzene rings lying in parallel planes.     

A two‐dimensional network in the molecular salt 2‐methylimidazolium hydrogen glutarate,and three‐dimensional networks in the salts 2‐methylimidazolium hydrogen succinate and 2‐methylimidazolium hydrogen adipate monohydrate

All three title compounds, C₄H₇N₂⁺·C₄H₅O₄⁻, (I), C₄H₇N₂⁺·C₅H₇O₄⁻, (II), and C₄H₇N₂⁺·C₆H₉O₄⁻·H₂O, (III), can be regarded as 1:1 organic salts. The dicarboxylic acids join through short acid bridges into infinite chains. Compound (I) crystallizes in the noncentrosymmetric Cmc2₁ space group and the asymmetric unit consists of a hydrogen succinate anion located on a mirror plane and a 2‐methylimidazolium cation disordered across the same mirror. The other two compounds crystallize in the triclinic P space group. The carboxylic acid H atom in (II) is disordered over both ends of the anion and sits on inversion centres between adjacent anions, forming symmetric short O...H...O bridges. Two independent anions in (III) sit across inversion centres, again with the carboxylic acid H atom disordered in short O...H...O bridges. The molecules in all three compounds are linked into two‐dimensional networks by combinations of imidazolium–carboxylate N⁺—H...O and carboxylate–carboxylate O—H...O hydrogen bonds. The two‐dimensional networks are further linked into three‐dimensional networks by C—H...O hydrogen bonds in (I) and by O_water—H...O hydrogen bonds in (III). According to the ΔpK_a rule, such 1:1 types of organic salts can be expected unambiguously. However, a 2:1 type of organic salt may be more easily obtained in (II) and (III) than in (I).     

A Novel Ruthenium(III) and Lithium Complex: Synthesis,Crystal Structure,and Magnetic Properties

A novel complex [Li₃{μ‐(H₂O)₆}(H₂O)₆]·[RuCl₆] has been synthesized and was characterized by single‐crystal X‐ray diffraction. The compound crystallizes in rhombohedral space group R3¯c, with the unit cell parameters a = b = 9.948(2)Å, c = 33.376(14)Å, γ = 120°, V = 2860.5(15)ų, Z = 6, D_c = 1.918 Mg m^—3, μ = 1.703 mm^—1, R = 0.0244, wR = 0.0478. The compound consists of a cation, which contains three lithium ions linked by six bridged water molecules, and an anion, which contains a ruthenium(III) ion. The whole complex can be described as a three‐dimensional structure linked by hydrogen bonds between cation and anion. The magnetic properties of the complex have been investigated. The IR, UV‐vis and EPR spectra are studied.     

Mixed Ligand Palladium(Ⅱ) Complex with NS-Bidentate S-Allyldithiocarbazate Schiff Base: Synthesis, Spectral Char-acterization, Crystal Structure and Decoding Intermolecular Interactions with Hirshfeld Surface Analysis

A new mixed ligand palladium(II) complex with bidentate NS‐donor chelate, [PdCl(PPh₃)L] (L: S‐allyl β‐N‐(benzylidene)dithiocarbazate), has been prepared and characterized using single crystal X‐ray diffraction and spectroscopic (electronic, IR, ¹H NMR and ¹³C NMR) techniques. The shorter Pd? P bond distance, 2.255(7) Å, than the sum of the single bond radii for palladium and phosphorus (2.41 Å), showed partial double bond character. Visualizing and exploring the crystal structure using Hirshfeld surface analysis showed the presence of π··· π, N··· π, C? H··· π, Cl···H and weak C? H···S interactions as most important intermolecular interactions in the crystal lattice, which are responsible to extension of the supramolecular network of the compound and stabilization of the crystal structure.