Conformational flexibility in amidophosphoesters: a CSD analysis completed with two new crystal structures of (C6H5O)2P(O)X [X = NHC7H13 and N(CH2C6H5)2] |
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Authors: | Banafsheh Vahdani Alviri Mehrdad Pourayoubi Abdul Ajees Abdul Salam Marek Ne
as Arie van der Lee Akshara Chithran Krishnan Damodaran |
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Affiliation: | Banafsheh Vahdani Alviri,Mehrdad Pourayoubi,Abdul Ajees Abdul Salam,Marek Nečas,Arie van der Lee,Akshara Chithran,Krishnan Damodaran |
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Abstract: | 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…π 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…π 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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Keywords: | amidophosphoester conformational flexibility Cambridge Structural Database crystal structure hydrogen bonding energy framework |
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