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Exploring short strong hydrogen bonds engineered in organic acid molecular crystals for temperature dependent proton migration behaviour using single crystal synchrotron X-ray diffraction (SCSXRD)

DOI: 10.1039/C9CE00925F DOI Help

Authors: Lucy K. Saunders (Diamond Light Source) , Harriott Nowell (Diamond Light Source) , Lauren E. Hatcher (University of Bath) , Helena J. Shepherd (University of Kent) , Simon J. Teat (Advanced Light Source) , David R. Allan (Diamond Light Source) , Paul R. Raithby (University of Bath) , Chick C. Wilson (University of Bath)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Crystengcomm , VOL 1014

State: Published (Approved)
Published: August 2019
Diamond Proposal Number(s): 18193

Open Access Open Access

Abstract: Seven multi-component molecular crystals containing O–H⋯O/O+–H⋯O− and N+–H⋯O− short strong hydrogen bonds (SSHBs) have been engineered by combining substituted organic acids with hydrogen bond acceptor molecules N,N-dimethylurea and isonicotinamide. In these materials, the shortest of the SSHBs are formed in the N,N-dimethylurea set for the ortho/para nitro-substituted organic acids whilst a twisted molecular approach favours the shorter SSHBs N+–H⋯O− in the isonicotinamide set. Temperature dependent proton migration behaviour has been explored in these systems using single crystal synchrotron X-ray diffraction (SCSXRD). By using a protocol which considers a combination of structural information when assessing the hydrogen atom (H-atom) behaviour, including refined H-atom positions alongside heavy atom geometry and Fourier difference maps, temperature dependent proton migration is indicated in two complexes (2: N,N-dimethylurea 2,4-dinitrobenzoic acid 1:1 and 5: isonicotinamide phthalic acid 2:1). We also implement Hirshfeld atom refinement for further confidence in this observation; this highlights the importance of having corroborating trends when applying the SCSXRD technique in these studies. Further insights into the SSHB donor–acceptor distance limit for temperature dependent proton migration are also revealed. For the O–H⋯O/O+–H⋯O− SSHBs, the systems here support the previously proposed maximum limit of 2.45 Å whilst for the charge assisted N+–H⋯O− SSHBs, a limit in the region of 2.55 Å may be suggested.

Subject Areas: Chemistry

Instruments: I19-Small Molecule Single Crystal Diffraction

Added On: 20/08/2019 10:46


Discipline Tags:

Chemical Engineering Organic Chemistry Engineering & Technology Chemistry

Technical Tags:

Diffraction Single Crystal X-ray Diffraction (SXRD)