Sławomir Domagała

Synthesis and characterization of 12-pyridinium derivatives of the [closo-1-CB11H12]- anion.

Diazotization of [closo-1-CB11H10-1-R-12-NH2](-)[NMe4](+) (4[NMe4]) in neat 4-methoxypyridine leads to 12-(4-methoxypyridinium) zwitterions [closo-1-CB11H10-1-R-12-(4-MeOC5H4N)] (2) in ∼50% yield. Demethylation of 2 with LiCl in dimethylformamide provides access to 12-pyridones 5[NMe4], which can be O-alkylated with alkyl triflates giving 12-(4-alkoxypyridinium) zwitterions, such as 1. This three-step process is more efficient than direct diazotization of amine 4[NMe4] in neat higher 4-alkoxypyridine. The new method was demonstrated for the synthesis of [closo-1-CB11H10-1-C5H11-12-(4-C7H15OC5H4N)] (1c), which exhibits a smectic A phase. Molecular and electronic structures of 4-methoxypyridinium zwitterion 2b and its C(1) isomer [closo-1-CB11H11-1-(4-MeOC5H4N)] (3b) were investigated by single-crystal X-ray diffraction and spectroscopic methods, respectively, and the experimental results were compared to those obtained with density functional theory methods. Lastly, the mechanism for formation of zwitterions 2 was investigated computationally revealing low energy for dediazoniation of the [closo-1-CB11H10-1-R-12-N2] (14) intermediate (ΔG298 ≈ 25 kcal/mol) to form boronium ylide 15, with weak dependence on substituent R. Dinitrogen derivative 14c was observed by (11)B NMR spectroscopy.

Determination of Experimental Charge Density in Model Nickel Macrocycle: [3,11-Bis(methoxycarbonyl)-1,5,9,13-tetraazacyclohexadeca-1,3,9,11-tetraenato-(2-)-κ4N]nickel(II)

Experimental and theoretical atomic charges and d-orbital populations were obtained for [3,11-bis(methoxycarbonyl)-1,5,9,13-tetraazacyclohexadeca-1,3,9,11-tetraenato(2-)-kappa(4)N]nickel(II) monocrystal (16Ni) using the Hansen and Coppens formalism. Several models of this structure were tested as a function of quality of the fit, convergence of the refinement, value of residual peaks and holes, and Hirshfelds rigid-bond test. The models with Ni-atomic scattering factors applied for the metal center are significantly better than those with the Ni-ionic scattering factors. The properties of the final electron density distributions are very consistent and similar for all of the models tested. The values of the d-orbital populations for Ni roughly agree with the occupation order of the d-electron levels for square-planar complexes derived from crystal field theory and are comparable with those obtained by the natural population analysis method. Experimental atoms-in-molecules charges calculated for four different models agree quite well for models with different symmetry restrictions and the same scattering factor for the Ni. Both experimental and theoretical methods predict relatively high negative values of charges for the nitrogen and oxygen atoms and also a quite high positive charge for the C(7) atom. The values of rho(r(BCP)) for the Ni-N bonds are in the range from 0.60 up to 0.75e A(-3), with positive laplacian values indicating noncovalent bonding. For the laplacian of the electron density evaluated in the plane of the macrocyclic ring, a typical map for a square-planar complex was obtained with four charge concentrations--3d(xy) orbitals--pointing toward the regions between the M-N bonds and charge depletions directed toward the (3,-1) critical points of the negative laplacian for the nitrogen atoms.

X-ray Diffraction, FT-IR, and 13C CP/MAS NMR Structural Studies of Solvated and Desolvated C-Methylcalix[4]resorcinarene

Solid C-methylcalix[4]resorcinarene solvated by acetonitrile and water (CAL-Me) and then modified by slow solvent evaporation (CAL-Me*) was studied using single-crystal and powder X-ray diffraction, FT-IR, and (13)C CP/MAS NMR. The CAL-Me solvate crystallizes in the monoclinic P2(1)/n space group with three CH(3)CN and two H(2)O molecules in the asymmetric part of the unit cell. The CAL-Me molecules adopt a typical crown conformation with all of the hydroxyl groups of the aryl rings oriented up and all of the methyl groups disposed down (the rccc isomeric form). The crystalline network is formed by resorcinarene, CH(3)CN, and H(2)O molecules and assembled by intermolecular hydrogen bonds and weak C-H...A or C-H...pi interactions. The desolvated CAL-Me* loses its crystalline character and becomes partly amorphous. It is devoid of CH(3)CN and deficient in water. However, the resorcinarene molecules still remain in the crown conformation supported by intramolecular hydrogen bonds, while intermolecular hydrogen bonds are considerably disintegrated. The work directs general attention to the problem of stability and polymorphism of resorcinarene solvates. It shows that the joint use of diffractometric and spectroscopic methods is advantageous in the structural studies of complex crystalline macromolecular systems. On the other hand, the solid-state IR and NMR spectroscopic analyses applied in tandem have been found highly beneficial to elucidate the disordered structure of poorly crystalline, desolvated resorcinarene.

Electronic and molecular structures and bulk second–order nonlinear optical properties of ferrocenyl ynones

Ferrocenyl ynones FcCOCCR (R = H, TMS, Ph) exhibit moderate second harmonic generation efficiencies in the solid state, whereas the methyl analog proved inactive. Their molecular structures and crystal packings were determined by single crystal X-ray diffraction, confirming that the inactive compound crystallizes in a centrosymmetric space group. The electronic structures of these compounds were studied experimentally (cyclic voltammetry, electronic absorption spectra) and theoretically (DFT and TD-DFT calculations). It appeared that the COCCR groups are stronger electron acceptors than the propionyl (COCH2CH3) group. Furthermore, these groups better stabilize metal-centred HOMO-2 to HOMO orbitals and lateral chain-centred LUMO orbitals and decrease HOMO-LUMO gaps. The TDDFT calculation of electronic transitions revealed that lower energy (LE) and higher energy (HE) bands observed in the electronic absorption spectra of compounds under study have more pronounced metal-to-ligand charge transfer character for ferrocenyl ynones than for propionylferrocene. The calculated static quadratic hyperpolarizabililities of ferrocenyl ynones are in the range ∼3 − 6 × 10−30 esu.

Aryl (ferrocenyl)-capped ethenylazaferrocenes: synthesis, structure and electrochemistry

The Horner–Wadsworth–Emmons reaction of 2,5-dimethylazaferrocene-1′-carbaldehyde with diethyl benzylphosphonate, diethyl p-methoxybenzylphosphonate and diethyl (ferrocenylmethyl)phosphonate afforded (E)-1-(2,5-dimethylazaferrocen-1′-yl)-2-phenylethene (2a), (E)-1-(2,5-dimethylazaferrocen-1′-yl)-2-(p-methoxyphenyl)ethene (2b) and (E)-1-(2,5-dimethylazaferrocen-1′-yl)-2-ferrocenylethene (2c), respectively. Cyclic voltammetry showed significant difference in the electrochemical behaviour of these compounds in comparison to their ferrocenyl counterparts. The styryl group, which is an electron-withdrawing group in the ferrocenyl compound, displays a reverse effect in the azaferrocenyl complex 2a. Introduction of the p-methoxystyryl group to 2,5-dimethylazaferrocene brings about a cathodic shift of the redox potential of 370 mV, whereas for the ferrocenyl analog the shift is only 60 mV. Compound 2c shows two redox waves due to two non-equivalent metallocenyl moieties, but there is only weak electronic coupling between redox centres. The W(CO)5-complex of 2c (4) was synthesised and its structure determined by X-ray diffraction.

Oxidative Coupling of Some 2,6-Disubstituted Phenol Derivatives in Perchloric Acid Mediated by Cerium(IV) Ions

Summary. 2,6-Disubstituted phenol derivatives have been oxidized by cerium(IV) perchlorate in aqueous or aqueous-acetonitrile solutions of perchloric acid as well as in two-phase systems to the corresponding 1,4-benzoquinones, 4,4′-diphenoquinones, and oligomeric poly(1,4-phenylene) oxides in good yield. Nature and constitution of the oxidation products as a consequence of reaction conditions and physico-chemical properties of radicals and radical ions are reported. These properties are discussed in terms of stabilities, pK values, and electron densities at carbon C4 and oxygen.Zusammenfassung. 2,6-Disubstituierte Phenolderivate wurden in wäßrigen oder wäßrig-acetonitrilischen Lösungen sowie in Zweiphasensystemen mittels Cer(IV)perchlorat zu den entsprechenden 1,4-Benzochinonen, 4,4′-Diphenochinonen und Poly(1,4-phenylen)oxiden oxidiert. Es wird über die Abhängigkeit der Art und Konstitution der Oxidationsprodukte von den Reaktionsbedingungen und den physikochemischen Eigenschaften der Radikale und Radikalionen berichtet. Die Ergebnisse werden im Zusammenhang mit Stabilitäten, pK-Werten und Elektronendichten an C4 und am Sauerstoff diskutiert.

Experimental and theoretical charge density assessments for the 4-perfluoropyridyl- and 4-perflurophenyl-1,2,3,5-dithiadiazolyl radicals

The results of an experimental density analysis of 4-perfluoropyridyl-1,2,3,5-dithiadiazolyl (NF-radical) are presented and compared with the previously reported analysis of the related 4-perfluorophenyl-1,2,3,5-dithiadiazolyl (F-radical). Both the NF- and F-radicals form dimers in their crystal lattice. The strong interaction between sulfur atoms in the dimers is confirmed by the high values of the electron density at the bond critical points. Some additional bond paths relating to weaker interactions are also observed in the dimers, notably between carbon atoms and between F and N atoms. For both radicals, the spin density is almost entirely located on the nitrogen and sulfur atoms of the dithiadiazolyl ring. However, the values of the spin density are higher in the case of the NF-radical, which may result in stronger interactions between sulfur atoms in the dimers. The electron density derived properties from the experimental and theoretical multipolar models are in fairly good agreement.

Oxidative cross-coupling of some 2,6- and N,N-disubstituted aniline derivatives with 4-aminophenol mediated by cerium(IV) ions in aqueous perchloric acid

SummaryThe mechanism of the oxidation of mixtures of 2,6-dimethylaniline (1), N,N-dimethylaniline (2), 2,6-diethylaniline (3), N,N-diethylaniline (4), N-methylaniline (5), 2,6-difluoroaniline (6), and 2,3,5,6-tetrafluoroaniline (7) with 4-aminophenol (8) by cerium(IV) ions in aqueous perchloric acid has been investigated. The indoaniline salts [O=C6H4=N-C6H2(R1)2NH(R2)2]+ClO4− (R1=H,R2=CH3, C2H5 orvice versa) are formed as intermediates in the cross-coupling reaction; they undergo oxidation to imino-4-benzoquinone (9) and its corresponding derivatives by cerium(IV) ions in high yields. The mechanism of this process is discussed.ZusammenfassungDie Oxidation von Mischungen von 2,6-Dimethylanilin (1), N,N-Dimethylanilin (2), 2,6-Diethylanilin (3), N,N-Diethylanilin (4), N-Methylanilin (5), 2,6-Difluoranolin (6) und 2,3,5,6-Tetrafluoranilin (7) mit 4-Aminophenol (8) durch Cer(IV)-Ionen in wässriger Perchlorsäure wurde untersucht. Als Zwischenprodukte der Kreuzkupplungsreaktion treten die Indoanilinsalze [O=C6H4=N-C6H2(R1)2NH(R2)2]+ClO4− (R1=H,R2=CH3, C2H5 oder umgekehrt) auf. Diese werden durch Cer(IV)-Ionen in hohen Ausbeuten zu Imino-4-benzochinon (9) und seinen entsprechenden Derivaten oxidiert. Der Mechanismus dieses Vorgangs wird diskutiert.

Magnetostructural Investigation of Orthogonal 1‐Aryl‐3‐Phenyl‐1,4‐Dihydrobenzo[e][1,2,4]triazin‐4‐yl Derivatives

3-Phenyl-1,4-dihydrobenzo[e][1,2,4]triazinyl radicals with the N(1) position substituted with naphth-2-yl (1 b), naphth-1-yl (1 c), pyren-1-yl (1 d), anthracen-9-yl (1 e), 2-trifluoromethylphenyl (1 f), 3-trifluoromethylphenyl (1 g), and 2-iodophenyl (1 h) were characterized by using single-crystal X-ray diffraction, variable-temperature magnetic susceptibility, and DFT computational methods. The substituent at N(1) is essentially orthogonal to the heterocycle plane in 1 f and 1 h, and with a high torsion angle in 1 c and 1 d. Radicals 1 c and 1 h form unusual infinite chains with crisscrossing hetero-co-facial π-π interactions, whereas radical 1 d forms analogous homo-co-facial arrangements. Infinite chains of homo-co-facial π-π dimers are found in 1 b, 1 f and 1 g; in the latter the position of the CF3 group controls the slippage of the dimers in the chain. No π-π parallel arrangements were found in 1 e. Magnetic susceptibility measurements demonstrated strong antiferromagnetic interactions in 1 b (J=-264±4 cm-1 ) and 1 f (J=-134±1 cm-1 ), while weak intradimer ferromagnetic interactions were found in 1 g (J2 =+21±1 and J1 =-15±1 cm-1 ). Other derivatives exhibit typical weak antiferromagnetic exchange interactions in a range of -5 to -10 cm-1 .

Rotaxanes composed of dibenzo-24-crown-8 and macrocyclic transition metal complexing tetraimine units

We present the structures of new rotaxanes. They are composed of dibenzo-24-crown-8 and an axle containing two tetraazamacrocyclic units coordinating the same, or different, metal ions (Ni or/and Cu). These units are linked with the m- and p-xylylene bridges. The structures of these compounds were confirmed by single crystal X-ray diffraction, NMR, and other spectroscopic methods. Rigid linkers between the macrocyclic units allow control of the axle length and geometry of the final compounds. The rotaxanes adopt one of two conformations: folded or extended. Rotaxanes are formed by simultaneous interactions of electron rich benzene rings with electron deficient six membered chelate rings and formation of hydrogen bonds between the secondary amino group and crown ether oxygens. Variable temperature 1H NMR studies of diamagnetic di-Ni-rotaxanes confirm that shuttling of the dibenzo-24-crown-8 moiety takes place along the p-xylylene linked axle, while folding of the axle in the m-xylylene linked rotaxane stabilizes the bent geometry of the whole compound and prevents shuttling of the crown ether moiety. In the case of rotaxanes containing the p-xylylene linkers, at elevated temperatures we observe a translocation of the crown ether unit between the metal coordinating macrocycles, which is well supported by electrochemical results for heteronuclear (Cu/Ni) systems but such translocation was not observed in the m-xylylene bridges. Electrochemical results suggest that an unfolding of the axle takes place upon oxidation of the metal centre in the di-Ni-rotaxane but not in heteronuclear m-xylylene linked rotaxanes.