Structure and Conformation of Novel BODIPY Ugi Adducts.

Two novel BODIPY-Ugi (boron dipyrromethene) adducts exhibit peculiar room temperature (T=20 °C) H-1 NMR spectra in that several protons located at the aromatic aniline-type ring are lost in the baseline. This observation revealed the existence of a dynamic conformational process where rotation around the C-N bond is hindered. Variable-temperature H-1 and C-13 NMR spectroscopic analysis confirmed this conclusion; that is, low-temperature spectra show distinct signals for all four aromatic protons below coalescence, whereas average signals are recorded above coalescence (T=+120 °C). Particularly interesting was the rather large difference in chemical shifts for the ortho protons below coalescence, Δδ=1.45 ppm, which was explained based on DFT computational analysis. Indeed, the calculated lowest-energy gas-phase conformation of the BODIPY Ugi adducts locates one half of the aniline-type ring in the shielding anisotropic cone of the bridge phenyl ring in the BODIPY segment. This is in contrast to the solid-state conformation established by X-ray diffraction analysis that shows a nearly parallel arrangement of the aromatic rings, probably induced by crystal packing forces.

Hydrogen-bond directionality and symmetry in [C(O)NH](N)2P(O)-based structures: a comparison between X-ray crystallography data and neutron-normalized values, and evaluation of reliability.

For [C(O)NH](N)2P(O)-based structures, the magnitude of the differences in the N-H...O, H...O=P and H...O=C angles has been evaluated when the N-H bond lengths, determined by X-ray diffraction, were compared to the neutron normalized values and the maximum percentage difference was obtained, i.e. about 3% for the angle even if the N-H bond lengths have a difference of about 30% (0.7 Šfor the X-ray and 1.03 Šfor the neutron-normalized value). The symmetries of the crystals are discussed with respect to the symmetry of the molecules, as well as to the symmetry of hydrogen-bonded motifs, and the role of the most directional hydrogen bond in raising the probability of obtaining centrosymmetric crystal structures is investigated. The work was performed by considering nine new X-ray crystal structures and 204 analogous structures retrieved from the Cambridge Structural Database.

Hirshfeld surface analysis of new phosphoramidates.

Hirshfeld surfaces and two-dimensional fingerprint plots are used to visualize and analyze intermolecular interactions in six new phosphoramidate structures, [2,6-F2-C6H3C(O)NH]P(O)[X]2 {X = N(C2H5)2 (1), [X]2 = NHCH2C(CH3)2CH2NH and with one CH3OH solvated molecule (2)}, [C6H5O]2P(O)Y [Y = NC4H8O (3), NHC6H4(3-Br) (4)] and [Z]2P(O)OP(O)[Z]2 [Z = N(CH3)(CH2C6H5) (5), NHC6H4(4-CH3) (6)]. Study of the short intermolecular contacts in structures (1)-(6) by Hirshfeld surfaces demonstrate that the O atom of P=O is a better H-atom acceptor than the O atom of C=O for (1) and (2), and also relative to the O atom of the C6H5O group for (3) and (4), and relative to the bridge O atom of the P(O)OP(O) segment for (5) and (6). The results confirm that the crystal packing is related to the kind of substituent linked to the P atom. Compounds (1), (2), (4) and (6), with characteristic N-H···O hydrogen bonds, show a pair of intense spikes (including the intermolecular H···O contacts) in the fingerprint plots, summarizing the major features of each structure in the related two-dimensional plot. For (3) and (5), without any N-H unit, the two short spikes are observed for (3) but are absent for (5). The upper d(e) and d(i) values (distances to the Hirshfeld surfaces for the nearest atoms outside and inside) in the fingerprint plots are more compact in (3) than in (4), and in (5) than in (6), reflecting the more efficient packing in (3) and (5). The tertiary N atoms of (3) and (5) do not take part in any intermolecular contacts involving H atoms. Moreover, structures (3)-(6) show greater contribution from C···H contacts relative to O···H contacts. Finally, Hirshfeld surfaces and fingerprint plots are employed for a comparison of the two independent molecules in the asymmetric unit of (1) and also, for a comparison of (6), in the orthorhombic crystal system, with the previously reported monoclinic polymorph (Pourayoubi, Fadaei et al., 2012).

Analysis of N-H···O hydrogen bonds in new C(O)-NH-P(O)-based phosphoric triamides and analogous structures deposited in the Cambridge Structural Database.

Five new compounds belonging to the phosphoric triamide family have been synthesized: two of them with the formula XC(O)NHP(O)Y [X = CF3 (1) and CClF2 (2), Y = NHCH2C(CH3)2CH2NH] involving a 1,3-diazaphosphorinane ring part, and three 2,6-Cl2C6H3C(O)NHP(O)Z2 phosphoric triamides [Z = NHC(CH3)3 (3), N(CH3)(C6H11) (4) and N(CH3)(CH2C6H5) (5)]. The characterization was performed by (31)P{(1)H}, (1)H, (13)C NMR, IR spectroscopy besides (19)F NMR for fluorine containing compounds (1) and (2), and X-ray single-crystal structure analysis for (1), (3), (4) and (5). In each molecule the P atom has a distorted tetrahedral environment. The N atoms bonded to P atom have mainly sp(2) character with a very slight tendency to a pyramidal coordination for some amido groups. Different types of N-H···O hydrogen bonds have been analyzed for (1), (3), (4) and (5) and 118 other structures (including 194 hydrogen bonds) deposited in the Cambridge Structural Database, containing either C(O)-NH-P(O)[N(C)(C)]2 or C(O)-NH-P(O)[NH(C)]2. The participation of N(CP)-H···O=P [N(CP) = the nitrogen atom of the C(O)-NH-P(O) fragment], N-H···O=P, N-H···O=C and N(CP)-H···O=C hydrogen bonds in different hydrogen-bonded motifs are discussed. Moreover, the involvement of the O atoms of C=O or P=O in the [N(CP)-H][N-H]···O=P, [N-H]2···O=P, [N-H]2···O=C and [N-H]3···O=C groups are considered. A histogram of N···O distances, the distribution of N-H···O angles and the scatterplot of N-H···O angles versus N···O distances are studied.