Myroslav O. Vysotsky

Novel electron-deficient 1,1′-binaphthol derivatives bearing two dicarboximide groups at the peri-positions show intense blue luminescence and aggregation-enhanced emission characteristics.

Calix[4]arenes fixed in the cone conformation and bearing four amino functionalities on the wide rim, are well known and often used starting materials in calixarene chemistry. During our studies in this field we have noticed, that the safe procedures known (which use palladium on carbon as catalyst and hydrazine hydrate as reducing agent in methanol at reflux) not always fit well for the synthesis of all possible even rather simple derivatives of this type and undesired mixtures are usual outcome in these cases. High resolution MS and 1H NMR indicate, that the main impurity (nearly 30%) is a partially reduced calix[4]arene containing three amino- and one nitro groups. We have modified the synthetic procedure by changing the solvent to iso-propanol, which allowed to shorten the reaction times and to obtain the desired products in high purity and yields.

The analysis of suit[2]-, suit[3]ane and tetrafould [2]-rotaxanes on the bases of calix[4]- arene with the help of the "mechanical disconnection operation" show that these structures possess only one mechanical bond, which is suggested to be called bi-, tri- and tetrafurcated one, respectively, since such structures bear two, three and four divergent mechanical entanglements. In the same time, introduction of the external bulky groups to these structures transforms such unique mechanical bonds into several single ones. There can be several different invariants which have only one mechanical bond, but possess different number of the intrinsic mechanical entanglements like, for example, in [2]-catenane and doubly braided [2]-catenane. The mechanical bond in the last case is proposed to be called the tight one. The constrictive bonds in carceplexes are classified as the spherical mechanical bonds. Thus, the whole classification of the mechanical bonds (together with the previously proposed ones), is presented.

Using results of X-ray diffraction study supramolecular architecture of crystals of 2-(4-iodophenyl)-1,10-phenanthroline has been analyzed on the basis of quantum-chemical calculations of intermolecular interactions energy. It is demonstrated that these crystals have three levels of organization. Molecules form stacked dimers with the highest binding energy (first level). These dimers represent basic unit of infinite columns stabilized by stacking interactions between dimers (second level). The energy of intermolecular interactions between neighbouring stacked columns is very close. This does not allow to figure out any layers in the crystal. Therefore crystals of this compound have columnar structure with almost isotropic packing of stacked columns (third level).

2-Mono- and 2,9-di-substituted 1,10-phenanthrolines with 4-pyridine units attached either via 1,4-phenylene- or 4-ethynyl-phenyl spacers, have been synthesised. The strategy is based on the introduction of 4-trimethylsilylphenyl group(s) at the phenanthroline core with the subsequent ipso-substitution of TMS groups by bromine or iodine and successive Suzuki or Sonogashira reactions with 4-pyridineboronic acid or 4-ethynylpyridine, respectively.

The trityl alcohols bearing three bromine or three iodine atoms at the para-positions of the aromatic units, have been known for more than a hundred years. In our case these compounds have been synthesized in one-pot sequence starting from the 1,4-dihalogenobenzenes via mono-lithiation and the successive reaction with diethylcarbonate. The compounds have been crystallized from different solvent mixtures leading to one structure of bromo- (A) and three structures of iodo trityl alcohols (B–D). The inclusion of dichloromethane (C) or benzene (D) in the crystalline lattices has been observed. In all cases the OH–π and halogen–π (and in one case the halogen-halogen and CH-O weak) contacts play crucial role in the crystal organisation. The common motif of the packing is the anti parallel arrangement of the trityl alcohol molecules into infinite chains. There is the gradual change in the intermolecular interactions going from the structures A and B, where only OH–π contacts between anti-parallel molecules are observed, to C with OH–π bifurcated contacts between anti-parallel molecules and further to the structure D, where practically no OH–π contacts are observed any longer. However in the case of D the splitting of the chain with anti-parallel molecules into two anti-parallel chains with parallelly assembled molecules takes place. These OH–π chains interact further with each other either via halogen–π or/and halogen–halogen, CH–O weak interactions. The shortest contacts found are 3.429 Å (1/A, Br–π) and 3.486 Å (2/D, I–π) while the longest contacts are 3.558 Å (1/A, Br–π) and 3.668 Å (2/B, I–π). No short contacts between the included solvent molecules and triiodo trityl alcohol within the structures C and D, have been observed. The quantum chemical calculations (DFT on the M05-2X/6-311G(d,p) level) gave the following interaction energies (kcal mol⁻¹) between two neighbouring molecules of one “OH–π chain”: −7.96 (A), −6.60 (B), −6.43 (C) and −6.45 (D), while the interaction energies via the halogen–π contacts vary from −2.17 to −3.58 kcal mol⁻¹ (per one contact).

Ten tetra-urea calix[4]arene derivatives with different ether residues (methyl, pentyl, benzyl, all combinations of methyl and pentyl, 1,3-dibenzyl-2,4-dipentyl), including also the tetrahydroxy compound and the 1,3-dipentyl ether, were synthesised. Their urea groups were substituted with a lipophilic residue to ensure sufficient solubility in cyclohexane. Thus, kinetics for the exchange of the included guest (benzene) against the solvent (cyclohexane) could be followed by ¹H NMR spectroscopy. The apparent first order rate constants decrease with increasing size of the ether residues from methyl to benzyl by more than three orders of magnitude. This can be understood by a decreasing flexibility/mobility of the calixarene skeleton. In line with this explanation is the rather slow exchange for the tetrahydroxy compound, where the cone conformation is stabilised by a cyclic array of intramolecular OH⋯OH hydrogen bonds.

The exclusive formation of hydrogen‐bonded dimers between tetraaryl and tetratosylurea calix[4]arenes has been used to prepare a series of ten “bisloop” tetraurea calix[4]arenes 3, in which adjacent phenylurea groups are covalently linked through α,ω‐dioxyalkane chains. This dimerization with tetratosylurea 2 as template preorganizes the alkenyl residues of tetra(m‐alkenyloxyphenyl) ureas 1 and enables their selective connection in high yield (up to 95 %) by olefin metathesis followed by hydrogenation. The “bisloop” calixarenes 3 also exclusively form heterodimers with 1. Thus, in a separated metathesis/hydrogenation sequence, a series of 14 cyclic bis[2]catenanes 4, in which two calix[4]arenes are connected through their wide rims by two pairs of interlocked rings (total size 29 to 41 atoms), were prepared in yields of up to 97 %. Optical resolution of these chiral bis[2]catenanes was studied by HPLC on chiral stationary phases. The single‐crystal X‐ray structure of one example (4(P,10)) confirmed the interlocking rings and revealed that the hydrogen‐bonded dimeric capsule of the calix[4]arene can be “completely” opened.