1. The Description of Non-Covalent Interactions in Terms of Bent´s Rule Sławomir J. Grabowski Faculty of Chemistry, University of the Basque Country UPV/EHU, and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Spain IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain e-mail: s.grabowski@ikerbasque.org

2. Studies on non-covalent interactions Rovira, C.; Novoa, J.J. Strength and Directianolity of the S…S Intermolecular Interactions, Chem. Eur. J. 1999, 5, 3689-3697 Braga, D.; Bazzi, C.; Grepioni, F.; Novoa, J.J. Electrostatic compression on non-covalent interactions : the case of π stacks involving ions, New.J.Chem. 1999, 23, 577. Müller-Dethlefs, Hobza, P, Noncovalent Interactions: A Challenge for Experiment and Theory, Chem. Rev. 2000, 100, 143-167 Hobza, P.; Müller-Dethlefs, K. Non-Covalent Interactions, Theory and Experiment, Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, 2010.

3. Lewis acid – Lewis base Electron charge transfer A-H +  … -  Bhydrogen bond A-H +  … -  H-Bdihydrogen bond A +  … -  H-Bhydride bond C-X +  … -  H-Bhalogen-hydride bond C-X +  … -  Bhalogen bond P.Lipkowski, S.J.Grabowski, J.Leszczynski J.Phys.Chem. A 2006, 110, 10296.

4. S.J.Grabowski, J. Phys. Chem. A 2011, 115, 12340–12347 S.J.Grabowski, J. Phys. Chem. A 2012, 116, 1838−1845

5. A-H…B hydrogen bond formation is a combination of two effects F. Weinhold, C. Landis, Valency and Bonding, A Natural Bond Orbital Donor – Acceptor Perspective, Cambridge University Press 2005 V. Alabugin, M. Manoharan, S. Peabody, F. Weinhold, J.Am.Chem.Soc. 2003, 125, 5973-5987 1.the hyperconjugative A-H bond weakening the charge transfer from the lone pair of B into the antibonding σ* orbital of the A-H bond often attributed to covalency of the hydrogen bond Reed, A.E.; Curtiss, L.A.; Weinhold, F. Chem.Rev. 1988, 88, 899-926. Sobczyk, L.; Grabowski, S.J.; Krygowski, T.M. Chem.Rev. 2005, 105, 3513-3560. Grabowski, S.J. Chem.Rev. 2011, 11, 2597-2625. 2.the rehybridization-promoted bond A-H strengthening. the increase of the s-character in the A-atom hybrid orbital of the A-H bond a consequence of Bent´s rule

6. According to Bent´s rule atoms maximize the s-character in hybrid orbitals aimed toward electropositive substituents and maximize their p-character in such orbitals aimed toward electronegative substituents H. A. Bent, Chem.Rev. 1961, 61, 275-311

7. F.Zordan et al., J.Am.Chem.Soc. 127 (2005), 5979-5989. Clark, T.; Hennemann, M.; Murray, J.S.; Politzer, P. J.Mol.Mod. 2007, 13, 291. Murray, J.; Concha, M.C.; Lane, P.; Hobza, P.; Politzer, P. J.Mol.Mod. 2008, 14, 699.

9. F 3 CCl…H 3 O + - CAHB(+) F 3 CCl…HF - HB F 3 CCl…HMgH - XHeB F 3 CCl…ClCH 3 – DXB F 3 CCl…OCH 2 - XB MP2/6-311++G(d,p) calculations

10. MoietyCl…A(B)C-Cl C-Cl…B(A)E bin OCH 2 3.0591.740 179.8 -1.42 Cl - 3.0981.721 180.0 -7.30 OH - 2.4601.734 175.5 -13.76 FCl2.9901.744 175.6 -0.43 ClCH 3 3.4671.745 168.8 -0.69 MgH 2 2.9641.742 169.4 -1.10 HF2.5921.758 96.6 -0.13 H3O+H3O+ 1.9791.795 94.1 -7.53 HCl 2 O + 1.7871.823 95.6 -9.02 Li+2.4821.773 78.7 -12.13 F 3 CCl-1.746 -- The chlorine – Lewis acid/Lewis base center distance (Cl…A(B), in Å), C-Cl bond length (Å), C-Cl…B(A) angle (degrees) as well as binding energy, E bin (corrected for BSSE, in kcal/mol).

11. MoietyEl trans C-chargeCl-chargePol(%C)s(%C) OCH 2 1.50.98440.031847.7627.27 Cl - 54.20.94260.096750.1829.96 OH - 123.40.91620.106051.8831.54 FCl2.20.99040.015447.2926.90 ClCH 3 6.00.99060.011647.2826.89 MgH 2 2.60.98820.023447.5327.16 HF-5.61.0021-0.012946.3825.95 H3O+H3O+ -122.71.03180.024144.2823.84 HCl 2 O + -221.71.05070.065242.2322.25 Li+-69.21.01220.011045.9925.4 F 3 CCl-0.99420.007347.026.62 El trans (in milielectrons) - the amount of electrons transferring, Pol(%C) - the CCl proton donating bond polarization (% at C-atom), s(%C) - the percentage s-character in C orbital of the CCl proton donating bond

14. Pol(%F) 79.3 S(%F) 24.2 Pol(%C) 50.4 S(%C) 43.0 Pol(%F) 77.6 S(%F) 20.7 Pol(%C) 47.9 S(%C) 41.1 Pol(%F) 78.6 S(%F) 23.3 Pol(%C) 49.8 S(%C) 42.7

15. Santiago de Compostela- WATOC 2011

16. Thank you for attention Financial support comes from Eusko Jaurlaritza (GIC 07/85 IT-330-07) and the Spanish Office for Scientific Research (CTQ2011-27374). Technical and human support provided by IZO-SGI SGIker (UPV/EHU, MICINN, GV/EJ, ESF) is gratefully acknowledged.