A group of bis(aryl)acenaphthenequinonediimine (Ar‐BIAN) ligands were synthesized through a modified procedure, which bypasses the need for absolutely dry conditions during the initial template synthesis. The molecular and electronic structure of the corresponding homoleptic [Cu(Ar‐BIAN)2]BF4 complexes were probed by means of a variety of spectroscopic methods. In accord with solution 13C NMR spectra, X‐ray crystallography reveals D2 or approximate D2 symmetry for the [Cu(p‐Cl‐BIAN)2]+ and [Cu(p‐Me‐BIAN)2]+ cations and noncrystallographic C2 symmetry for the [Cu(o‐Ph‐BIAN)2]+ cation. The structures of the p‐Cl‐, p‐Me, and o‐Ph‐BIAN complexes agree with the presence of ligands in their neutral form according to the lengths of the relevant C–C and C=N bonds of the organic skeleton. The concerted stereo–electronic effects of the substituents on the aryl rings affect the electron donor/acceptor capacities of the ligands and the structures of the complexes, as the study of the visible absorption spectra of the complexes indicates. The spectra of the complexes are dominated by intense and broad metal‐to‐ligand charge transfer (MLCT) bands that enter the near‐infrared (NIR) region. Additionally, electrochemical studies undertaken reveal several successive electron capture and release processes, which further manifest the redox versatility of the ligands.

No abstract

The molecular recognition process and the ability to form multicomponent supramolecular systems have been investigated for the amide of triphenylacetic acid and l-tyrosine (N-triphenylacetyl-l-tyrosine, TrCOTyr). The presence of several supramolecular synthons within the same amide molecule allows the formation of various multicomponent crystals, where TrCOTyr serves as a chiral host. Isostructural crystals of solvates with methanol and ethanol and a series of binary crystalline molecular complexes with selected organic diamines (1,5-naphthyridine, quinoxaline, 4,4′-bipyridyl, and DABCO) were obtained. The structures of the crystals were planned based on non-covalent interactions (O–H···N or N–H+···O− hydrogen bonds) present in a basic structural motif, which is a heterotrimeric building block consisting of two molecules of the host and one molecule of the guest. The complex of TrCOTyr with DABCO is an exception. The anionic dimers built off the TrCOTyr molecules form a supramolecular gutter, with trityl groups located on the edge and filled by DABCO cationic dimers. Whereas most of the racemic mixtures crystallize as racemic crystals or as conglomerates, the additional tests carried out for racemic N-triphenylacetyl-tyrosine (rac-TrCOTyr) showed that the compound crystallizes as a solid solution of enantiomers.

p‐Phenylenediamine can be obtained as the dihydrate, C6H8N2·2H2O, (I), and in its anhydrous form, C6H8N2, (II). The asymmetric unit of (I) contains one half of the p‐phenylenediamine molecule lying about an inversion centre and two halves of water molecules, one lying on a mirror plane and the other lying across a mirror plane. In (II), the asymmetric unit consists of one molecule in a general position and two half molecules located around inversion centres. In both structures, the p‐phenylenediamine molecules are arranged in layers stabilized by N—H...π interactions. The diamine layers in (I) are isostructural with half of the layers in (II). On dehydration, crystals of (I) transform to (II). Comparison of their crystal structures suggests the most plausible mechanism of the transformation process which requires, in addition to translational motion of the diamine molecules, in‐plane rotation of every fourth p‐phenylenediamine molecule by ca 60°. A search of the Cambridge Structural Database shows that the formation of hydrates by aromatic amines should be considered exceptional.

No abstract

Two new six-coordinated high-spin Co(II) complexes have been synthesized through the reactions of Co(II) salts with dipyridylamine (dpamH) and 5-nitro-salicylaldehyde (5-NO2-saloH) or 3-methoxy-salicylaldehyde (3-OCH3-saloH) under argon atmosphere: [Co(dpamH)2(5-NO2-salo)]NO3 (1) and [Co(dpamH)2(3-OCH3-salo)]NO3·1.3 EtOH·0.4H2O (2). According to the crystal packing of compound 1, two coordination cations are linked with two nitrate anions into a cyclic dimeric arrangement via N-H···O and C-H···O hydrogen bonds. In turn, these dimers are assembled into (100) layers through π-π stacking interactions between inversion-center related pyridine rings of the dpamH ligands. The crystal packing of compound 2 reveals a 1D assembly consisting solely from the coordination cations, which is formed by π-π stacking interactions between pyridine rings of one of the dpamH along the [010] and another 1D assembly of the coordination cations and nitrate anions through the N-H···O hydrogen-bonding interactions along the [001] direction. All complexes were magnetically characterized, and a new approximation method was used to fit the magnetic susceptibility data in the whole temperature range 2-300 K on the basis of an empirical expression which allows the treatment of each cobalt(II) ion in axial symmetry as an effective spin S(eff) = 1/2. In zero-field, dynamic magnetic susceptibility measurements show slow magnetic relaxation below 5.5 K for compound 2. The slow dynamics may originate from the motion of broad domain walls and is characterized by an Arrhenius law with a single energy barrier Δr/k(B) = 55(1) K for the [10-1488 Hz] frequency range. In order to reveal the importance of the crystal packing in the SCM behavior, a gentle heating process to 180 °C was carried out to remove the solvent molecules. The system, after heating, undergoes a major but not complete collapse of the network retaining to a small percentage its SCM character.

No abstract

In this study, three new zinc(II) complexes with 5-substituted salicylaldehyde ligands (X-saloH) (X = 5-chloro, 5-nitro and 5-methyl) with the general formula [Zn(X-salo)(2)(CH3OH)n], (n = 0 or 2) were synthesized. An octahedral geometry was found for both the complexes [Zn(5-NO2-salo)(2)(CH3OH)(2)] and [Zn(5-Cl-salo)(2)(CH3OH)(2)] by single-crystal X-ray diffraction analysis. These complexes were characterized also by spectroscopy (IR and H-1-NMR). Simultaneous TG/DTG-DTA techniques were used to analyze their thermal behavior under inert atmosphere, with particular attention to determine their thermal degradation pathways, which was found to be a multi-step decomposition accompanied by the release of the ligand molecules. Finally, the kinetic analysis of the decomposition processes was performed by applying both the isoconversional Ozawa-Flynn-Wall (OFW) and the Kissinger-Akahira-Sunose (KAS) methods