Abstract
Saturated acyclic four-atom groups closed with a classic intramolecular hydrogen bond, generating planar five-membered rings (hydrogen-bridged quasi-rings), in which at least one of the ring atoms is bonded to other non-ring atoms that are not in the ring plane and, thus, capable to form intermolecular interactions, were studied in this work, in order to find the preferred mutual positions of these species in crystals and evaluate strength of intermolecular interactions. We studied parallel interactions of these rings by analysing crystal structures in the Cambridge Structural Database (CSD) and by quantum chemical calculations. The rings can have one hydrogen atom out of the ring plane that can form hydrogen bonds between two parallel rings. Hence, in these systems with parallel rings, two types of hydrogen bonds can be present, one in the ring, and the other one between two parallel rings. The CSD search showed that 27% of the rings in the crystal structures form parallel interactions. The calculations at very accurate CCSD(T)/CBS level revealed strong interactions, in model systems of thiosemicarbazide, semicarbazide and glycolamide dimers the energies are −9.68, −7.12 and −4.25 kcal/mol. The hydrogen bonds between rings, as well as dispersion interactions contribute to the strong interaction energies.
Highlights
The Cambridge Structural Database (CSD) search showed that 27% of the rings in the crystal structures form parallel interactions
The aim of this work was to deepen the knowledge about intermolecular interactions of hydrogen-bridged rings by analyzing interaction of the saturated acyclic four-atom groups closed by a classic hydrogen bond, generating planar five-membered quasi-rings, with formed at least rings canintramolecular participate in C–H ̈ π interactions similar to aromatic organic molecules
To get an insight into the interactions of the hydrogen-bridged rings without multiple bonds that planar groups in the ring, we found 978 rings in the CSD, while 27% (264) of the rings formed have non-planar groups in the ring (Figure 1a), search and analysis of the data in crystal structures parallel interactions [46]
Summary
The stacking interactions between aromatic rings are one of the well examined non-covalent interactions [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21]. The interaction energies of nickel and copper six-membered chelate rings with benzene, calculated at very acurate CCSD(T)/CBS level, are4.77 and6.39 kcal/mol respectively [43,44], remarkably stronger than stacking interaction between two benzene molecules, ́2.73 kcal/mol [10]. Supramolecular chemistry of hydrogen-bridged quasi-ring species becomes very interesting from the fundamental point of view, it could be useful in molecular recognition, crystal engineering or biochemistry. Interactions of hydrogen-bridged rings in supramolecular arrangements are similar to interactions of classical rings formed by covalent bonding.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
