Hydrogen-bonded mesomorphic complexes combining hydrophilic and fluorophilic molecular segments

A 2,4-diamino-6-phenyl-1,3,5-triazine carrying a single oligo(ethylene oxide) (EO) chain has been investigated in binary mixtures with two-chain and three-chain semiperfluorinated benzoic acids. Mixtures of the triazine with three equivalents of the complementary acids exhibit a hexagonal columnar (Col_h) mesophase. Docking of three acid molecules to the diaminotriazine nucleus leads to the formation of disc-like aggregates with a central hydrogen-bonded polar core surrounded by the peripheral fluoroalkyl chains, which self-assemble in columns arranged on a hexagonal lattice. The polar EO chains at the triazine cores do not segregate into a distinct sub-space but are included into the polar cores, providing increased flexibility of the cores with respect to conformations and available hydrogen bonding sites. In equimolar (1 : 1) triazine/benzoic acid mixtures macroscopic phase separation of excess triazine from the columnar LC phases occurs. These Col_h phases are formed by [1 : 3] or [2 : 4] complexes, depending on the number of fluorinated chains. However, some of the excess triazine component is accommodated within the polar column cores, contributing to space filling and providing additional hydrogen bonding along the columns. Thus the EO chain, despite of being fixed at the periphery, assemble in the core region of the aggregates, this is distinct from the self-assembly of related alkyl or semiperfluoroalkyl substituted diaminotriazines with fluorinated benzoic acids, forming discrete disc-like [1 : 3] or rod-like [1 : 1] complexes. Obviously, the flexible EO chains decrease the effect of the aggregate shape on self-assembly and lead to an increased contribution of general amphiphilicity to self-assembly.

2-D and 3-D porous structures from tetrakis(4-thyminylmethylphenyl)methane

Using tetraphenylmethane as a scaffold, a potent hub for generation of organic porous networks has been synthesized by introduction of thymine functionalities in all para-positions.

Thymine functionalised porphyrins, synthesis and heteromolecular surface-based self-assembly

The synthesis and surface-based self-assembly of thymine-functionalised porphyrins is described. Reaction of 1-formylphenyl-3-benzoyl-thymine with suitable pyrollic species leads to the formation of tetra-(phenylthymine)porphyrin (tetra-TP) or mono-thymine-tri-(3,5-di-tert-butylphenyl)porphyrin (mono-TP). Single crystal X-ray diffraction studies demonstrate the self-association of mono-TP in the solid state through thymine···thymine hydrogen-bonding interactions but in solution this interaction (Kd = 6.1 ± 3.0 M-1) is relatively weak in comparison to the heteromolecular interaction between mono-TP and 9-propyladenine (K = 91.8 ± 20.5 M-1). STM studies of the tetratopic hydrogen-bonding tecton, tetra-TP, deposited on an HOPG substrate reveal the formation of an almost perfectly square self-assembled lattice through thymine···thymine hydrogen-bonding. Co-deposition of tetra-TP with 9-propyladenine leads to the adoption of preferable thymine···adenine interactions leading to the formation of a heteromolecular tetra-TP···9-propyladenine hydrogen bonded array including both Watson-Crick thymine···adenine interactions and adenine···adenine hydrogen-bonding. The studies demonstrate a pathway for the self-assembly of tetratopic hydrogen-bonding tectons and the use of preferential heteromolecular thymine···adenine interactions for the disruption of the homomolecular tetra-TP array. Studies of the self-assembly of tetra-TP and 9-propyladenine demonstrate a strong dependence on overall concentration and molar ratio of components indicating the importance of kinetic effects in surface self-assembly processes.

On the role of DMSO-O(lone pair)⋯π(arene), DMSO-S(lone pair)⋯π(arene) and SO⋯π(arene) interactions in the crystal structures of dimethyl sulphoxide (DMSO) solvates

DMSO-O(lone pair)⋯π(arene), DMSO-S(lone pair)⋯π(arene) and SO⋯π(arene) interactions are found in DMSO solvates.

Infinite copper(II) coordination architectures from a resonative aminotriazine-derived tripodal ligand: synthesis, structures, and magnetic properties

The ligand 2,4,6-tris(2-picolylamino)-1,3,5-triazine (o-H3tpat) with essentially resonative structure and two copper(II)-based one-dimensional coordination chain structures, [Cu3Cl5(o-H2tpat)(H2O)]·MeOH·CH2Cl2 (1) and [Cu2(o-H2tpat)(H2O)(MeOH)(NO3)2](NO3)·3MeOH (2), with different structural patterns have been synthesized and characterized using single crystal X-ray diffraction analysis. For o-H3tpat, two crystalline forms showing different solid-state structural features are obtained from MeOH/Et2O (form I) and CH2Cl2/Et2O (form II), respectively. The o-H3tpat form I adopts an asymmetric-configured all-amino resonative tautomer with three cis-trans-trans-arranged pyridyl groups, whereas the o-H3tpat form II adopts also an identical resonative structure but where two of the three pyridyl groups are in a cis-manner and the third one is nearly coplanar with the central aminotriazine core. On the other hand, the designed tripodal ligand in both Cu(II)-complexes serves as a monoanion, o-H2tpat(-), which suits a propeller-configured all-imino resonative structure in 1 and a syn-anti-configured amino-imino-imino resonative structure in 2. These observations significantly indicate that the o-H3tpat ligand can self-adjust and interconvert its conformation via a possible structure transformation associated with proton-shift to adapt a change in the crystallization and self-assembly reaction systems. In the magnetic point of view, 1 is treated as repeated chains composed of infinite {Cu6Cl10} units wherein the hexanuclear unit is further decomposed to one {Cu(II)4Cl6} and two magnetically isolated {Cu(II)Cl2} subunits. Antiferromagnetic interactions are found for the Cu4 subunits (g = 2.33, 2J1 = -5.6 cm(-1), 2J2 = -8.6 cm(-1), 2J3 = -4.1 cm(-1), and J4 held to zero). For 2, it is considered as an infinite chain that composes of Cu2 units antiferromagnetically coupled (g = 2.03, 2J1 = -0.2 cm(-1)). The small antiferromagnetic exchange constants in both 1 and 2 suggest that the unpaired spins do not effectively interact through the tripodal o-H2tpat(-) ligands.