The Sodium (Iso)Cyanurates Na_x[H_3–xC₃N₃O₃]·yH₂O (x = 1–3, y = 0, 1): A Key‐Series for Understanding the Crystal Chemistry of Metal (Iso)Cyanurates

Abstract

The (iso)cyanurates ] were synthesized phase pure from Na 2 CO 3 ·10H 2 O, NaOH, and cyanuric acid, respectively, in aqueous solution by carefully adjusting the crystallization conditions. The crystal structures of all compounds were determined by single-crystal X-ray diffraction {Na 2 [HC 3 N 3 O 3 ]·H 2 O: P1, a = 3.51660(10) Å, b = 7.8300(3) Å, c = 11.3966(4) Å, α = 86.4400(10)°, β = 85.5350(10)°, γ = 85.0720(10)°, Z = 2, R 1 = 0.030, wR 2 = 0.078; Na 2 [HC 3 N 3 O 3 ]: Pnma, a = 6.3409 (6) Å, b = 12.2382(13) Å, c = 6.5919(7) Å, Z = 4, R 1 = 0.045, wR 2 = 0.079; * Prof. Dr. H. A. Höppe E-Mail: henning@ak-hoeppe.de [a] 257 Na 3 [C 3 N 3 O 3 ]: R3c, a = 11.7459(3) Å, c = 6.5286(3) Å, Z = 3, R 1 = 0.039, wR 2 = 0.066}. The structures show ribbons (Na[H 2 C 3 N 3 O 3 ]·H 2 O), dimers (Na 2 [HC 3 N 3 O 3 ]·H 2 O), chains (Na 2 [HC 3 N 3 O 3 ]), or columns (Na 3 [C 3 N 3 O 3 ]) of hydrogen-bonded and parallel stacked (iso)cyanurate anions.These motifs are shown to be characteristic for certain degrees of protonation and hydration, and all (iso)cyanurate crystal structures found so far were classified accordingly. X-ray powder patterns, thermogravimetry curves, IR and UV/Vis spectra were measured for all compounds.According to the X-ray powder diffraction pattern ( Figure S3, Supporting Information), we were able to synthesize phase

Two Light‐Metal Dihydrogenisocyanurate Hydrates Linked by Diagonal Relationship: Syntheses, Crystal Structures, and Vibrational Spectra of Li[H2N3C3O3]·1.75 H2O and Mg[H2N3C3O3]2·8 H2O

“…The vibration frequencies obtained from the IR and Raman spectra (Figure ) of the title compounds coincide well to those reported for the rich variety of other alkali‐ and alkaline‐earth metal isocyanurate hydrates, e.g. in references, , and therefore confirm the presence of isocyanurate moieties in both investigated compounds.…”

“…The ribbons themselves consist of both crystallographically independent dihydrogenisocyanurate anions, which occur alternatingly, so that the well‐known one‐dimensional sequence of isocyanurate anions with four linking hydrogen atoms per unit results , . These ribbons contain formally isolated moieties, but due to their strong N–H ··· O hydrogen bonds, they form nearly planar (angle between neighboring isocyanurate planes: 1.1°) one‐dimensional infinite ribbons 1 ∞ {[H 2 N 3 C 3 O 3 ] – }, whose planes are arranged perpendicularly to the cationic layers 2 ∞ {[[Mg(OH) 2 ) 6 ] · (H 2 O) 6/3 ] 2+ } (Figure ).…”

“…To the best of our knowledge, a plethora of alkali‐ and alkaline‐earth metal cyanurates or cyanurate hydrates have been reported and characterized, but the monoclinic compound Li 2 [HN 3 C 3 O 3 ] · 2 H 2 O was the only one containing only Li + or Mg 2+ , respectively. Exploiting a review paper by Seifer , we started to reproduce the reported synthesis for lithium and magnesium cyanurates in order to elucidate, if the diagonal relationship prevails under these conditions or if the general trend of “the higher the charge‐to‐radius quotient is, the more hydrated the cation becomes”, will be confirmed.…”

Biuret—A Crucial Reaction Intermediate for Understanding Urea Pyrolysis To Form Carbon Nitrides: Crystal‐Structure Elucidation and In Situ Diffractometric, Vibrational and Thermal Characterisation

“… [58] The molecule features one intramolecular hydrogen bond between one carbonyl and one amide group (O−H distance: 1.92 Å), as well as two intermolecular hydrogen bonds between amide and carbonyl groups towards each of the two adjacent, coplanar biuret molecules, forming two sets of skew ribbons ubiquitous in the crystal chemistry of ureas (Figure 1 b). [51, 59–62] The ribbons within a set are stacked antiparallel offset with a inter‐ribbon distance of about 3.3 Å, roughly corresponding to the sum of the van der Waals radii of N/O and C. One set of these ribbons traverses the unit cell roughly parallel to [10 ], the other parallel to [14 11 ], with a dihedral angle of about 53.5° between the two ribbon planes, resulting in a criss‐cross pattern with rhombical channels along (11 0 6) (Figure 1 c). The diameter of the resulting channel corresponds to the inter‐ribbon distance, so the crystal structure can be regarded as close packed.…”

Cs3Na(H2C3N3O3)4·3H2O: A Mixed Alkali‐Metal Hydroisocyanurate Nonlinear Optical Material Containing π‐Conjugated Six‐Membered‐Ring Units

“…Hydroisocyanurates, namely monobasic (H 2 C 3 N 3 O 3 ) – , dibasic (HC 3 N 3 O 3 ) 2– and the neutral H 3 C 3 N 3 O 3 , were expected to show large birefringence and strong SHG response as well. Up to now, several hydroisocyanurates have been developed including alkali metals, alkaline earth metals, and transition metal compounds such as Na 2 [HC 3 N 3 O 3 ] · H 2 O, K 2 (HC 3 N 3 O 3 ), Rb[H 2 C 3 N 3 O 3 ] · H 2 O, Cs[H 2 C 3 N 3 O 3 ] · 0.5H 2 O, Sr[H 2 C 3 N 3 O 3 ] 2 · 4H 2 O, and Ba 3 [H 2 C 3 N 3 O 3 ] 2 [HC 3 N 3 O 3 ] 2 · 4H 2 O, etc . Unfortunately, most of them crystallize in centrosymmetric structures without SHG effects, except for the dibasic KLi(HC 3 N 3 O 3 ) · 2H 2 O (KLHCY) found by Ye's group recently .…”