title: Schiff base macrocycles containing pyrroles and pyrazoles.
abstract: A double nucleophilic substitution reaction of 3,5-bis(chloromethyl)pyrazole with pyrroles generates a novel pyrrole-pyrazole hybrid building block, the pyrazole analogue to tripyrrane. Vilsmeier-Haack formylation produces the corresponding dialdehyde, which was used in the formation of a series of nonaromatic Schiff base macrocycles. NMR and UV/Vis spectroscopy and single-crystal diffractometry were used to characterize the novel macrocycles. The solid-state structures of select free bases and protonated members of this class of macrocycles display a range of intra- and intermolecular hydrogen-bonding patterns that suggest their use in molecular-recognition systems. They also contain an acid-sensitive chromophore. Their acid-base and anion-recognition properties were ascertained; alas, only modest anion-selective spectroscopic signatures could be detected by using UV/Vis and (1)H NMR spectroscopy. The macrocycles proved resistant toward oxidation to their aromatic congeners. The pyrrole-pyrazole building blocks presented are potentially useful for the synthesis of a range of pyrazole analogues of all-pyrrole macrocycles.
authors.affiliation: Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, 37077 Göttingen, Germany.
authors.forename: Stamatia
authors.initials: S
authors.lastname: Katsiaouni
authors.forename: Sebastian
authors.initials: S
authors.lastname: Dechert
authors.forename: Raymond P
authors.initials: RP
authors.lastname: Briñas
authors.forename: Christian
authors.initials: C
authors.lastname: Brückner
authors.forename: Franc
authors.initials: F
authors.lastname: Meyer