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Exploring Cyanoacetylene Oligomers: Insights into Cyano-Substituted Cyclobutadienes and Dewar Benzenes

This study investigates the intriguing world of cyanoacetylene oligomers, particularly focusing on cyano-substituted cyclobutadienes and Dewar benzenes. Authors from the University of Wisconsin, Technische Universität Braunschweig, and Gottfried-Wilhelm-Leibniz-Universität Hannover present experimental findings and theoretical analyses, exploring the stability and reaction pathways of these molecules. Key details include their formation, computed energies using the B3LYP/6-31G* method, and implications for astrochemistry and molecular recognition. Join us to delve into these captivating nano-scale compounds.

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Exploring Cyanoacetylene Oligomers: Insights into Cyano-Substituted Cyclobutadienes and Dewar Benzenes

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  1. Studies of Cyanoacetylene Oligomers: Cyano-SubstitutedCyclobutadienes, Dewar-Benzenes, and Benzenes Jessica L. Menke Robert J. McMahon—University of Wisconsin, MadisonHenning Hopf—Technische Universität Braunschweig, Braunschweig, Germany Jens-Uwe Grabow—Gottfried-Wilhelm-Leibniz-Universität, Hannover, Germany Midwest Astrochemistry Meeting University of Illinois November 8, 2008 Image from www.nasa.gov

  2. Cyano-Containing Molecules in the ISM & Titan’s Atmosphere Herbst, E. J. Phys. Chem. A 2005, 109, 4017; Young, Y. L. Icarus1987, 72, 468; Strobel, D. F. Int. Rev. Phys. Chem.1983, 3, 145; Mizutani, H. Origins of Life1975, 6, 513; Becker, R. S.; Hong, J. H. J. Phys. Chem.1983, 87, 163; Herbst, E. Chem. Soc. Rev.2001, 30, 168.

  3. Interesting/Unexpected Experimental Results Witulski, B.; Ernst, L.; Jones, P. J.; Hopf, H Angew. Chem. Int. Ed. Engl.1989, 28, 1279. Hopf, H.; Witulski, B Pure & Appl. Chem.1993, 65, 47. Breitkopf, V.; Hopf, H.; Klärner, F.-G.; Witulski, B.; Zimmy, B. Liebigs Ann.1995, 613.

  4. Proposed Reaction Pathway 4 Not seen experimentally Relative energies (kcal/mol) computed using B3LYP/6-31G* level with ZPVE corrections Witulski, B.; Ernst, L.; Jones, P. J.; Hopf, H Angew. Chem. Int. Ed. Engl.1989, 28, 1279. Hopf, H.; Witulski, B Pure & Appl. Chem.1993, 65, 47. Breitkopf, V.; Hopf, H.; Klärner, F.-G.; Witulski, B.; Zimmy, B. Liebigs Ann.1995, 613.

  5. Photochemical Formation of Cyano-Benzenes 5 Guillemin, J. C.; Ferris, J. P. European Space Agency, [Special Publication], SP, 1992, ESA-SP-338 177. Woods, P. M.; Millar, T. J.; Zijlstra, A. A.; Herbst, E. Astrophys. J. 2002, 574, L167.

  6. Computed Rotational Constants and Dipole Moments 6 Rotational Constants (GHz) Rotational Constants (cm-1) Dipole Moment (D) 1.41295 55.9434 0.88410 18.8926 7.51 0.54380 14.1232 1.86607 42.3591 0.63019 25.2125 3.78 0.47110 16.3027 0.90219 27.0469 0.90219 27.0469 0.00 0.45109 13.5233 Computed at the B3LYP/6-31G* level Wohlfart, K.; Schnell, M.; Grabow, J.-U.; Kupper, J. J. Mol. Spectrosc.2008, 247, 119.

  7. Isolation of Various Cyclobutadienes 7 Isolated Masamune, 1977 Matrix Isolated Peterson, 1997 Isolated Maier, 1988 Matrix Isolated Krantz, 1973 Isolated Cram, 1991 “Self Destructive Molecule Lives Longer in Prison” Isolated Gompper, 1968 Image: Cram, D. J.; Cram, J. M. Container Molecules & Their Guests, Royal Soc. Of Chemistry: Great Britain, 1994, 209. Quote: Milgrom, L. J. Inclusion Phenom. Mol. Rcognit. Chem.1992, 13, 97.

  8. Cyano-Substitution Effects on Cyclobutadiene 8 n = 0 n = 1 0.0 -9.4 n = 2 -15.3 -15.3 -14.5 Relative energies (kcal/mol) computed using B3LYP/6-31G* level without ZPVE corrections n = 3 n = 4 Order of Stabilization tBu < H < CN < SiH3 < Me < SiMe3 -17.8 -18.4 Maier, G.; Neudert, J.; Wolf, O.; Pappusch, D.; Sekiguchi, A.; Tanaka, M.; Matsuo, T. J. Am. Chem. Soc.2002, 124, 13819. Balci, M.; McKee, M. L.; Schleyer, Paul von Rague J. Phys. Chem. A2000, 104, 1246.

  9. Cyano-Substitution Effects on Cyclobutadiene Singlet-Triplet Gaps 9 Triplet S-T gap Singlet aS-T Gap < 0 = singlet ground state. bCorrected for ZPV energies.

  10. Current/Future Studies 10 Krantz, A.; Lin, C. U.; Newton, M. D. J. Am. Chem. Soc. 1973, 95, 2744. Chapman, O. L.; De la Cruz, P.; Roth, R.; Pacansky, J. J. Am. Chem. Soc.1973, 95, 1337. Bell,G. A.; Dunkin, I. R.; Shields, C. J. Spectrochin. Aceta, Part A, 1985, 41A, 1221. Webster, O. W. J. Am. Chem. Soc.1966, 88, 4055.

  11. Acknowledgements 11 • Robert J. McMahon • The McMahon Group • Nikki Burrmann • Katherine Traynor • Chris Shaffer • Laura Kopff • Brian Esselman • Alex Nolan • Matt Biller • Jeff Slosarxzyk • Dr. Caroline Pharr • Dr. Phillip Thomas • NSF for funding Lady Liberty on Lake Mendota, Lake Mendota, University of Wisconsin, Madison

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