Interaction of morpholine and thiomorpholine with molecular diiodine:X-ray crystal structure of morpholinium triiodide

Intriguing Case ofPseudo-Isomorphism between Chiral and Racemic Crystals of rac- and (S)/(R)2-(1,8-Naphthalimido)-2-quinuclidin-3-yl, and Their Reactivity Toward I2and IBr

“…The XRD data obtained for the adducts 3 and 4 allow to calculate n values of 0.64 and 0.62, respectively (i.e., at the borderline between type 1 and type 2 adducts). However, the presence of two stretching bands, observed in the Raman spectra of the synthesized adducts (Figure and Figure SI-5 of the Supporting Information) at about 110 cm –1 (ν 1 symmetric N–I–I stretching) and 150 cm –1 (ν 3 antisymmetric N–I–I stretching), not present in the donors, suggests the existence of a N–I–I three-body system, according to the assignments proposed by Arca et al…”

“…18 On the basis of the I−I bond distance (d) and bond order (n) (which may be estimated according to the Pauling's equation 19 ), the I 2 -adducts may be classified into weak or medium-weak adducts (type 1 D•••I 2 adducts; d in the 2.72− 2.85 Å range, n > 0.6) and strong adducts (type 2 D−I−I threebody system adducts; d about 2.90 Å, bond orders of both D−I and I−I in the 0.4−0.6 range), according to Deplano et al 18 The XRD data obtained for the adducts 3 and 4 allow to calculate n values of 0.64 and 0.62, respectively (i.e., at the borderline between type 1 and type 2 adducts). However, the presence of two stretching bands, observed in the Raman spectra of the synthesized adducts (Figure 13 and Figure SI-5 of the Supporting Information) at about 110 cm −1 (ν 1 symmetric N−I−I stretching) and 150 cm −1 (ν 3 antisymmetric N−I−I stretching), not present in the donors, suggests the existence of a N−I−I three-body system, according to the assignments proposed by Arca et al 20 From this point-of-view, the I 2 -adducts under study appear significantly different from those obtained by other authors using other N-donors, since they show N•••I distances shorter than most complexes reported in the literature, 21 according to the strong n → σ* donor character of quinuclidine, related to the high pK a value of its conjugate acid. 22 Pyridine-, pyrazine-, and quinoxaline-based donors have been reported to be characterized by N•••I distances significantly higher than ours (i.e., 2.562, 2.817, and 2.994 Å, respectively); 23−25 not unexpectedly, these adducts show in their Raman spectra a single band, 23,24 in agreement with their weak nature.…”

P282: Antenatal diagnosis of placenta accreta with Color Doppler and magnetic resonance imaging

“…In comparison to hydrogen bonds, which usually involve a modest number of acceptor atoms (typically O or N), the set of halogen‐bond acceptors is larger, encompassing, among others, O, N, S, and Se 16. With our interest in exploring halogen bonds involving atoms heavier than oxygen, we decided to construct cocrystals using tetrafluoro‐1,4‐diiodobenzene (tfib) as a halogen‐bond donor17 and readily available sulfur‐containing molecules 1,4‐thioxane (tox) and 1,4‐thiomorpholine (tmo) as the acceptors (Scheme ) 18. We anticipated that cocrystallization of tfib with either tox or tmo would result in the formation of one‐dimensional polymer chains of alternating donor and acceptor molecules, held together by halogen bonds (Scheme ).…”