Quadratate Und Hydrogenquadratate Cyclischer Stickstoffbasen Mit Schicht-, Ketten- und Leiterstrukturen / Squarates and Hydrogensquarates of Cyclic Nitrogen Bases with Layer-, Chainand Ladder-Structures

Abstract

Abstract The synthesis and single crystal X-ray structures of four adducts of squaric acid with cyclic nitrogen bases are reported. Extensive hydrogen bonding, ionic interactions and (in one case) π-π-interactions lead to layered, and to two- and three-dimensional assemblies. [Pyrimidinium][ hydrogenquadratate] (1) has a layer structure, consisting of head-to-tail infinite chains of pyrimidinium and [HC4O4]− ions, which are cross-linked by short N-H···O and C-H···O hydrogen bonds. [C9H11N2][HC4O4] ・0.5H2C4O4 (2), the adduct of a benzodiazepin and squaric acid, has a ladder-structure. Chains of [HC4O4]− ions and H2C4O4 molecules in alternating order form the ladder-beam. Layers of cations and anions in the ratio 2:1 build the crosspieces at an angle of 49° to the beam. The layers contain dimers of [HC4O4]− ions. [H2L2][HC4O4]2 (3) with L2 = 5,6,7,8,9,14,15,16,17,18-decahydrodibenzo[e,l]-1,4,8,11-tetraaza-cyclotetradecine shows zigzag chains made of [HC4O4]− ions. Between the [H2L2]2+ and the [HC4O4]− ions π-π interactions exist besides up to four N-H···O hydrogen bonds. The [H2L2]2+ ions possess two different conformations. [H2cyclam][C2O4] ·4H2O (4) contains strongly undulated layers of the composition [C4O4 ·4H2O]2−. The cations, which show two intramolecular N-H···N hydrogen bonds with N···N distances of 2.870 (3) Å , are interlinked at an angle of 41.5°.