Publication details

Conformational flexibility in amido­phospho­esters: a CSD analysis com­pleted with two new crystal structures of (C6H5O)2P(O)X [X = NHC7H13 and N(CH2C6H5)2]


ALVIRI Banafsheh Vahdani POURAYOUBI Mehrdad SALAM Abdul Ajees Abdul NEČAS Marek VAN DER LEE Arie CHITHRAN Akshara DAMODARAN Krishnan

Year of publication 2020
Type Article in Periodical
Magazine / Source Acta Crystallographica Section C: Structural Chemistry
MU Faculty or unit

Faculty of Science

Keywords amidophosphoester; conformational flexibility; Cambridge Structural Database; crystal structure; hydrogen bonding; energy framework
Description The crystal structures of diphenyl (cyclo­heptyl­amido)­phosphate, C19H24NO3P or (C6H5O)2P(O)(NHC7H13), (I), and diphenyl (di­benzyl­amido)­phosphate, C26H24NO3P or (C6H5O)2P(O)[N(CH2C6H5)2], (II), are reported. The NHC7H13 group in (I) provides two significant hydrogen-donor sites in N—H...O and C—H...O hydrogen bonds, needed for a one-dimensional hydrogen-bond pattern along [100] in the crystal, while (II), with a (C6H5CH2)2N moiety, lacks these hydrogen bonds, but its three-dimensional supra­molecular structure is mediated by C—H...? inter­actions. The conformational behaviour of the phenyl rings in (I), (II) and analogous structures from the Cambridge Structural Database (CSD) were studied in terms of flexibility, volume of the other group attached to phospho­rus and packing forces. From this study, synclinal (±sc), anti­clinal (±ac) and anti­periplanar (±ap) conformations were found to occur. In the structure of (II), there is an intra­molecular Cortho—H...O inter­action that imposes a +sc conformation for the phenyl ring involved. For the structures from the CSD, the +sc and ±ap conformations appear to be mainly imposed by similar Cortho—H...O intra­molecular inter­actions. The large contribution of the C...H/H...C contacts (32.3%) in the two-dimensional fingerprint plots of (II) is a result of the C—H...? inter­actions. The differential scanning calorimetry (DSC) analyses exhibit peak temperatures (Tm) at 109 and 81 °C for (I) and (II), respectively, which agree with the strengths of the inter­molecular contacts and the melting points.
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