Crystal Engineering Studies of the Complexes of Ethyl Resorcinarene with Aromatic Nitrogen Heterocycles

Abstract

Five X-ray structures of complexes of ethyl resorcinarene with aromatic nitrogen heterocycles (imidazole, 1,2,4-triazole, pyridine, pyrazine, 2-pyridylmethanol and quinoline) show that ethyl resorcinarene spontaneously forms molecular inclusion complexes with five- and six-membered aromatic nitrogen heterocycles via π ⃛π and CH ⃛π interactions. However, with 10-membered quinoline, no molecular inclusion complex is formed. Instead, quinoline manifests crystal lattice inclusion.

Keywords:

• Crystal engineering
• X-ray diffraction
• Resorcinarenes
• Complexation
• Nitrogen heterocycles

Acknowledgements

We thank Dr D. Falàbu for synthesizing compound 1 and crystallizing 8. The financial support of Academy of Finland (project no. 100319) is gratefully acknowledged by M.N.

Notes

^†The distances between the centroids of the opposite benzene rings are in accordance with earlier reported values of solid state structures of resorcinarenes in the crown conformation [18–20]. In the solid state, the conformation is usually not a perfect crown but slightly pinched.

^‡ {\rm Ct01 = C1 -- C6,} {\rm Ct02 = C8 -- C13,} {\rm Ct03 = C15 -- C20,} {\rm Ct04 = C22 -- C27.}

The Future of Supramolecular ChemistryAt present, Supramolecular Chemistry is greatly influenced by X-ray structure determinations of single crystals of supramolecular systems. Detailed structural information plays a crucial role in evaluation of weak intermolecular (e.g. supramolecular) intercations and functions and acts as a feedback to the synthesis planning and molecular design. These features will gain even more importance in the future when intelligent and functional nano-machines and -motors are to be designed, prepared and structurally characterized. The importance of supramolecular crystal engineering as a research area of its own will grow in the future since the first reports about dynamic behavior of close-packed crystal lattices have already been presented (Science 2002, 298, 1000). New functional crystalline materials will be developed, based on the increased knowledge on intermolecular interactions and the facts influencing the crystallization. Rational design of functional materials and devices will continue to rely on the expertise of crystal engineering and X-ray structural determinations.Kari Rissanen was born in 1959. He undertook Chemistry studies at the University of Jyväskylä, 1980–1985 and remained there for his MSc in Organic Chemistry 1985, and PhD in Chemistry (Solid-state Structural Chemistry of Organic Compounds), 1990. He was Chemistry Assistant and Assistant Professor, at University of Jyväskylä, 1985–1993, and Research Fellow (1988–1991) and Senior Research Fellow (1991–1993), Finnish Academy. In 1993, he became Associate Professor, Organic Chemistry, University of Joensuu, Finland and in 1995 moved to his current position as Professor and Head of Laboratory of Organic Chemistry, University of Jyväskylä, Finland; since 1987, he has published ca. 200 publications in scientific journals, 14 patents/patent applications and >100 posters/lectures in scientific conferences in the field of Structural and Synthetic Supramolecular and Organic Chemistry.