Search

CSD refcodes and additional plots from the CSD search: distribution of relevant distances and torsion and dihedral angles. EP distribution within different crystal structures containing the o-dialkoxybenzene fragment. Examples of crystal structures with multiple hydrogen bonding interactions to O···O systems. Figure S1. Distribution of torsion angle O1a−C3a−C3b−O1b showing the preferentially coplanar arrangement of the two ether oxygen atoms with respect to the benzene ring. Figure S2. Plot of torsion angles C1a−O1a−C3a−C3b vs. C1b−O1b−C3b−C3a. Figure S3. Additional fragments used in CSD search. Figure S4. Distribution of corresponding O...O distances in transition metal complexes. Figure S5. Distribution of angles: C4-C3-O1 and O1-C3a-C3b i.e. O1-C3b-C3a in the extracted crystal structures shows significant deviation from the expected value of 120°. Figure S6. Distribution of dihedral angles between the C3/O1/C1 planes reflects the coplanar orientation of the oxygen electron pairs in the extracted crystal structures. Figure S7. Laplacian distribution in relevant planes of DMB system. Fugre S8. Comparison of the negative EP isosurfaces of DMB and anisole. Figure S9. EP distribution in meta- and para-DMB. Figure S10. Examples of EP distribution in different crystal structures containing the odialkoxybenzene fragment. Figure S11. Examples of multiple hydrogen bonding interactions to O...O system (O…H ≤ 3.0 Å and D−H...O ≥ 110°). Figure S12. CSD-based spatial distribution of D–H donors around O…O system. IsoStar plots are given for D–H…O interactions with O…H distances up to 2.6 Å. Figure S13. Distribution of O…H distances from O–H…O and N–H…O interactions. Figure S14. Distribution of the H atoms belonging to OH/NH donor groups with respect to the O…O acceptor plane (P1). Figure S15. Molecular graph showing the bond paths and bond critical points corresponding to the interactions of O...O acceptor system in crystal structures: RABWIA, FOTKUW and ITUCEG. Figure S16. Sca

Statistical analysis of data extracted from the Cambridge Structural Database (CSD) has been used to investigate the crystal structure properties of odialkoxybenzene derivatives, compounds containing two ether oxygen acceptors in ortho positions of benzene ring. It has been shown that in more than 90% of cases, the fragment has predictable geometrical characteristics where the two ether oxygens form short interatomic O center dot center dot center dot O contact (2.57 A in average), while O-substitutents take trans position, both approximately coplanar with the benzene ring. Such arrangement of oxygen acceptors produces a large and uniform area of the negative electrostatic potential suitable for multiple hydrogen bonding. The acceptor abilities of the O center dot center dot center dot O system have been investigated by the statistical CSD analysis. The ab initio estimation of the interaction energy in the dimer of o-dimethoxybenzene (DMB) and H2O, employed as a model system, is achieved via high-level electron correlation CCSD(T) calculation with the complete basis set extrapolation. The interaction energy is estimated to be 6.5 kcal/mol. The results indicate the existence of a very flat potential the region between methoxy oxygens and that DMB water is a highly flexible system. The structural role of the O center dot center dot center dot O acceptor system is particularly interesting considering its ability to form multiple hydrogen bonding

Theoretical charge density analysis of the thioureido based compound 4-methyl-3-thiosemicarbazide (MeTSC) is used in this study with the aim to provide additional insight into electronic features of the thioureido sulfur acceptor and the corresponding D-H...S hydrogen bonding (D=N, C). The present work is motivated by our earlier experimental charge density study on the same compound that pointed out to a great flexibility of the thioureido S acceptor and its ability to adjust the lone pair electron density to the donor groups in simultaneous hydrogen bonding. Through the additional theoretical approach we were able to single out different fragments of MeTSC crystal and to carefully follow the changes in electron density properties of the S acceptors belonging to: isolated MeTSC monomers (i.e. two crystallographically independent molecules), eight D-H...S bonded dimers and MeTSC molecules placed in full crystal environment, where each S atom engages in four hydrogen bonds. Deformation density of the sulfur's lone electron pair, topological properties of D-H...S interactions and electrostatic potential are here examined in order to comprehend the mutual influence and potential cooperative effects of the four simultaneously formed interactions to each of the S acceptors. The hydrogen bonding involving thioureido S acceptor is also investigated in terms of the energetic properties of the eight real MeTSC dimers existing in the crystal structure, and additional systems MeTSC/MeOH and acetone/MeOH. The latter systems are designed with the purpose of direct comparison and ranking of interactions involving thioureido S to those involving more conventional, carbonyl O acceptor. Energetic features were thoroughly studied through electrostatic interactions energies (XD2006), cohesive energies (CRYSTAL09) and ab initio approach employing the coupled-cluster single S and doubles augmented by a perturbational correction for connected triple excitations (CCSD(T)) method.