[15]Crown-5: An Unsymmetrical Bifacial Hydrogen-Bond Acceptor in Crystal Engineering

Abstract

Reaction of [15]crown-5 with erbium nitrate and a range of nickel salts results in the formation of the hydrogen-bonded chain species [Er(NO 3 ) 3

[M(H2O)2(15-crown-5)](NO3)2: A System Rich in Polymorphic and Modulated Phases

“…The only structure in the CSD with a Ni 2+ ion complexed by a 15-crown-5 ligand (refcode BIHFED) was reported in a meeting abstract only and was archived without coordinates. We have, however, found seven phases containing Ni 2+ , 2NO 3 -, 15-crown-5, and water (including the compound 23 but the Ni 2+ ion is not coordinated by the crown ligand in any of them. Two additional phases containing these three components are known, but these last two phases also include a solvent molecule (e.g., acetonitrile) that was included in the synthesis in an attempt to reduce the number of water ligands coordinated to the Ni 2+ ion.…”

Packing Problems: High Z′ Crystal Structures and Their Relationship to Cocrystals, Inclusion Compounds, and Polymorphism

“…185 These compounds are further examples of the tendency for [15]-crown-5 complexes to exhibit complex low symmetry crystal packing behavior. 186 While a transition from dynamic behavior to an ordered, modulated structure is a clear way in which Z′ can increase, this is by no means the only situation. The interesting Z′ = 12 structure of 4-ethynyl-N,N-dimethylaniline (32) exhibits a reversible, single-crystal to single-crystal, phase transition at around 123 K between two different Z′ = 12 forms.…”

“…Indeed it turned out that other metal aqua complex cocrystals with 15-crown-5 also display high Z′ behavior such as the Z′ = 4 structure of [Er(NO 3 ) 3 (H 2 O) 3 ]·(15-crown-5)·H 2 O. 186 Despite this structural explanation, however, a particularly intriguing aspect of the structure of 33 is its preparation, which involved the very slow loss of HCl from the precursor oxonium complex 5 over a period of 6 weeks within a liquid clathrate medium (Figure 26b). Had this very gradual crystallization process allowed the structure to form optimal interactions of low symmetry?…”

Solid-State Binding Studies of Group 2 Metal Ions with 12-Crown-4Dedicated to Professor Joachim Strähle on the Occasion of his 65thBirthday

“…competes favourably against water for a position in the coordination sphere [19,40,41]. competes favourably against water for a position in the coordination sphere [19,40,41].…”