Crystal structures and theoretical calculations of two peculiar compounds derived from 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one

• Novel pyrazoline derivative potassium coordination polymer and organic salt.
• Various effects of coordination and intermolecular weak interactions was compared.
• Pyrazoline anions in the two compounds have the different conformations.
• The coplanarity of the two O atoms depends on their coordination environment.
• The sites for coordination and hydrogen bonding was predicted by calculations.

A potassium coordination polymer [K2(PMBP)2(H2O)3]n·2nH2O (1) was prepared by reaction of 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HPMBP) with potassium hydroxide. The single crystal of the supermolecule C6H11NH3+·PMBP− (2) was then obtained by utilizing cyclohexylamine as the proton acceptor. It is a diketonate salt with an organic base where the PMBP− anions are stabilized by the intermolecular weak interactions (including hydrogen bonding, π–π stacking interactions and Van der Waals forces), rather than by coordination to a metal centre. Geometrical parameters of the isolated PMBP− anion were optimized through quantum chemistry calculation to simulate the state without any disturbances or interactions. Comparison of geometric parameters of compound 1 with the optimized structure of PMBP− provides an approach to study weak intermolecular interactions in the crystal state. The coordination sites and the proton acceptors of hydrogen bonds predicted by theoretical calculations are consistent to the experimental results.

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