Adam Duong

Using Pyridinyl-Substituted Diaminotriazines to Bind Pd(II) and Create Metallotectons for Engineering Hydrogen-Bonded Crystals

The pyridinyl groups of pyridinyl-substituted diaminotriazines 3a,b and 4a,b can bind metals, and the diaminotriazinyl (DAT) groups serve independently to ensure that the resulting complexes can participate in intercomplex hydrogen bonding according to characteristic motifs. As planned, ligands 3a,b and 4a,b form trans square-planar 2:1 complexes with PdCl(2), and further association of the complexes is directed in part by hydrogen bonding of the DAT groups. Similarly, ligands 3a,b and 4a,b form cationic square-planar 4:1 complexes with Pd(BF(4))(2), Pd(PF(6))(2), and Pd(NO(3))(2), and the complexes again typically associate by hydrogen bonding of the peripheral DAT groups. The observed complexes have predictable constitutions and shared structural features that result logically from their characteristic topologies and the ability of DAT groups to engage in hydrogen bonding. These results illustrate the potential of a hybrid inorganic/organic strategy for constructing materials in which coordinative bonds to metals are used in conjunction with other interactions, both to build the molecular components and to control their organization.

Two-dimensional molecular organization of pyridinecarboxylic acids adsorbed on graphite.

Pyridinecarboxylic acids 3-9 are adsorbed from solution onto graphite to produce well-ordered adlayers that can be imaged by scanning tunneling microscopy. Hydrogen bonds involving the carboxyl groups and the nitrogen atom of the pyridyl ring play key roles in controlling the observed two-dimensional (2D) organization. Pyridinecarboxylic acids have a strong tendency to associate to form hydrogen-bonded chains and cyclic oligomers, which then pack to produce sheets. The preference for sheets ensures that molecular organization in 2D and 3D typically shows a significant degree of homology. Together, our observations highlight the potential of engineering similarly ordered 2D and 3D structures built from simple compounds that combine an inherent affinity for surfaces with an ability to engage in strong coplanar intermolecular interactions.

Engineering homologous molecular organization in 2D and 3D. Cocrystallization of aminoazines and alkanecarboxylic acids

Amino-substituted azines such as aminotriazines have simple planar structures with an affinity for adsorption on graphite. In addition, aminoazines associate predictably with carboxylic acids according to a reliable hydrogen-bonded motif. Together, these properties help predispose aminoazines and alkanecarboxylic acids to cocrystallize and to coadsorb on graphite to give related 3D and 2D structures built from essentially planar tapes. These results illustrate how molecular materials that reliably adopt similar ordered structures in both adlayers and bulk samples can be devised by choosing components that combine an affinity for surfaces with a tendency to form sheets held together by strong coplanar intermolecular interactions.

Bis(2,2′-bipyrimidine-κ2N1,N1′)palladium(II) bis­(tetra­fluoro­borate) acetonitrile monosolvate

The reaction of [Pd(MeCN)4](BF4)2 with 2,2′-bipyrimidine (bpm) in MeCN–CHCl3 afforded the title compound, [Pd(C8H6N4)2](BF4)2·C2H3N. The asymmetric unit contains two half complexes, with the PdII atoms both lying on a twofold axis. Each metal atom adopts a tetrahedrally distorted square-planar geometry. In the crystal, [Pd(bpm)2] dications are linked by C—H⋯N hydrogen bonds, forming chains parallel to the b axis. The chains are further linked by C—H⋯F and C—H⋯N interactions involving the tetrafluoroborate anions and acetonitrile molecules. In this way, each chain interacts with six surrounding chains to generate the observed three-dimensional structure.

trans-Dichloridobis[(pyridin-4-yl)boronic acid-κN]palladium(II) dimethyl sulfoxide disolvate.

In the title compound, [PdCl2(C5H6BNO2)2]·2C2H6OS, the PdII ion is located on an inversion centre and is four-coordinated in a trans square-planar geometry by two chloride ions and two (pyridin-4-yl)boronic acid ligands. The Pd—N and Pd—Cl distances are 2.023 (2) and 2.2977 (7) Å, respectively, and the average N—Pd—Cl angle is 90°. The dimethyl sulfoxide solvent molecules play a key role in the crystal structure by bridging the complex molecules via O—H⋯O hydrogen bonds, forming tapes running along the b axis. C—H⋯O interactions also contribute to the cohesion of the crystal.