Experimental Charge Density Study on an Ionic Crown Ether Complex: [Kc18-Crown-6]+N3-.cntdot.H2O

Unexpected Structural Diversity in Alkali Metal Azide‐Crown Ether Complexes: Syntheses, X‐ray Structures, and Quantum‐Chemical Calculations

“…Only one example was structurally characterised, in a charge density study of [K( [18]crown-6)(N 3 )(H 2 O)], in which interest was focussed on the K-( [18]crown-6) interaction. [9] As part of an investigation into polynitrogen species, we report here the synthesis and X-ray crystal structures of a range of such complexes. DFT calculations have been carried out to compute the minimum-energy structures and infrared spectra of these systems.…”

“…Similar hydrogen-bonded networks have been studied in some detail in sodium [18]crown-6 complexes with a variety of anions. [26] DFT calculations were only performed on the [Na( [15 [9] so only the structure of [Rb( [18]crown-6)(N 3 )(H 2 O)] was determined in this work. The structure of the [K( [18]crown-6)(N 3 )(H 2 O)] complex taken from reference [9] is shown in Figure 3a, where it is compared with the computed DFT structures obtained in this work for the monomer (Figure 3b) and the dimer (Figure 3c).…”

“…[26] DFT calculations were only performed on the [Na( [15 [9] so only the structure of [Rb( [18]crown-6)(N 3 )(H 2 O)] was determined in this work. The structure of the [K( [18]crown-6)(N 3 )(H 2 O)] complex taken from reference [9] is shown in Figure 3a, where it is compared with the computed DFT structures obtained in this work for the monomer (Figure 3b) and the dimer (Figure 3c). Comparison of the computed structures shown in Figure 3b and Figure 3c shows that on going from the monomer to the dimer a flattening of the N 3 unit occurs, which is consistent with the structure found experimentally.…”

“…These KÀN terminal bond lengths are computed as 2.784 and 2.905 (the experimental value from ref. [9] is 2.896 ( 2)). Experimentally, the KÀO ring distances are in the range 2.78-2.97 , and this is also the case in the computed dimer structure.…”

Low-cost conversion of a coaxial nozzle arrangement into a stationary low-temperature attachment

“…Cooling the specimen during data collection significantly reduces the thermal motion of atoms (Brock & Dunitz, 1990). The electron-density map is notably higher resolved, facilitating the location of H-atom positions and electron-deformation density studies (Koritsanszky, Buschmann, Luger, Knochel & Patz, 1994). Nowadays, a variety of low-temperature attachments based on gas-stream cooling are commercially available (Cosier & Glazer, 1986;Stoe Diffraction Systems, 1987; EnrafNonius, MSC/Rigaku and Siemens also offer low-temperature attachments).…”