Very Strong C−H···O, N−H···O, and O−H···O Hydrogen Bonds Involving a Cyclic Phosphate

Abstract

Very short C-H...O, N-H...O, and O-H...O hydrogen bonds have been generated utilizing the cyclic phosphate [CH2(6-t-Bu-4-Me-C6H2O)2]P(O)OH (1). X-ray structures of (i) 1 (unsolvated, two polymorphs), 1...EtOH, and 1...MeOH, (ii) [imidazolium](+)[CH2(6-t-Bu-4-Me-C6H2O)2PO2](-)...MeOH [2], (iii) [HNC5H4-N=N-C5H4NH](2+)[(CH2(6-t-Bu-4-Me-C6H2O)2PO2)2](2-)...4CH3CN...H2O [3], (v) [K, 18-crown-6](+)[(CH2(6-t-Bu-4-Me-C6H2O)2P(O)OH)(CH2(6-t-Bu-4-Me-C6H2O)2PO2)](-)...2THF [4], (vi) 1...cytosine...MeOH [5], (vii) 1...adenine...1/2MeOH [6], and (viii) 1...S-(-)-proline [7] have been determined. The phosphate 1 in both its forms is a hydrogen-bonded dimer with a short O-H...O distance of 2.481(2) [triclinic form] or 2.507(3) A [monoclinic form]. Compound 2 has a helical structure with a very short C-H...O hydrogen bond involving an imidazolyl C-H and methanol in addition to N-H...O hydrogen bonds. A helical motif is also seen in 5. In 3, an extremely short N-H...O hydrogen bond [N...O 2.558(4) A] is observed. Compounds 6 and 7 also exhibit short N-H...O hydrogen bonds. In 1...EtOH, a 12-membered hydrogen-bonded ring motif, with one of the shortest known O-H...O hydrogen bonds [O...O 2.368(4) A], is present. 1...MeOH is a similar dimer with a very short O(-H)...O bond [2.429(3) A]. In 4, the deprotonated phosphate (anion) and the parent acid are held together by a hydrogen bond on one side and a coordinate/covalent bond to potassium on the other; the O-H...O bond is symmetrical and very strong [O...O 2.397(3) A].

Magnetische Molekülverbindungen: Schaltung magnetischer Eigenschaften durch externe Stimuli

“…Durch Kombination eines organischen Radikals (in dem Fall eines Carbens) mit den 3d-Spins eines Metallions wurden molekulare Heterospin-Magnete erzeugt. [123][124][125][126][127][128] Unter anderem wurden eindimensionale ferri-und ferromagnetische Ketten, [124,128] ein Heterospin-System mit Spinglasverhalten [126] und ein Einzelmolekülmagnet [127] [127] 5. ¾nderungen magnetischer Eigenschaften bei photochromen Reaktionen…”

Synthesis and Application of a Bidentate Ligand Based on Decafluoro‐3‐phenyl‐3‐pentanol: Steric Effect of Pentafluoroethyl Groups on the Stereomutation of O‐Equatorial C‐Apical Spirophosphoranes

“…These O‐equatorial phosphoranes isomerized irreversibly to their stable stereoisomers (O‐apical) at elevated temperatures, indicating that the O‐equatorial isomers are kinetic products. There are several examples of isolated phosphoranes exhibiting “reversed apicophilicity” 4i–k. 13, 14 Notably, by introducing very bulky bidentate ligands, some of these phosphoranes became thermodynamically stable species even though the regular configurations were allowed, and a new insight into apicophilicity was unveiled from the unique system 4i–k.…”

Comparison of Anionic and Lewis Acid Stabilized N‐Heterocyclic Oxoboranes: Their Facile Synthesis from a Borinic Acid

“…The short BÀO bond observed in 3 b, along with the almost trigonal-planar geometry of the boron atom (sum of angles 359.98 (18)8), is indicative of a B À O double bond. [15] The geometric features of the hydrogen bond are comparable to those found in imidazolium aryloxides. The O1···C30 separation of 2.847 (O1ÀH30 1.898 ; C30-H30-O1 176.518) indicates a strong hydrogen bond between the anion and cation.…”

“…The O1···C30 separation of 2.847 (O1ÀH30 1.898 ; C30-H30-O1 176.518) indicates a strong hydrogen bond between the anion and cation. [15] The geometric features of the hydrogen bond are comparable to those found in imidazolium aryloxides. [16] C À H···X hydrogen bonds between imidazolium cations and heteroatomic anions in ionic liquids (ILs) have been experimentally and theoretically studied extensively in recent years owing to their significant effects on the properties of imidazolium ILs.…”