Volume 4, Issue 4, Pages 795-806 (April 2018) Longest C–C Single Bond among Neutral Hydrocarbons with a Bond Length beyond 1.8 Å  Yusuke Ishigaki, Takuya Shimajiri, Takashi Takeda, Ryo Katoono, Takanori Suzuki  Chem  Volume 4, Issue 4, Pages 795-806 (April 2018) DOI: 10.1016/j.chempr.2018.01.011 Copyright © 2018 Elsevier Inc. Terms and Conditions

Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 1 The Compounds in This Paper Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 2 Theoretical Studies (M06-2X/6-31G*) of Newly Designed Derivatives 10a–10c and DSAP (A–C) Front (A), side (B), and top (C) views of optimized structure for 10a. (D–F) Front (D), side (E), and top (F) views of optimized structure for 10b. (G–I) Front (G), side (H), and top (I) views of optimized structure for 10c. (J–L) Front (J), side (K), and top (L) views of optimized structure for DSAP. (M) Energy potentials (dotted lines) and d1 values (solid lines) for 10c (red) and DSAP (blue) were calculated by varying the torsion angle α in steps of 2.5° and by considering metastable (ΔE = 0.66 kcal mol−1 for 10c) or the most stable conformations. (N) Torsion angles α and d1 values of fully optimized structures for 10a–10c and DSAP. Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 3 Raman Spectra of 10c (A) A spectrum (red) measured with a single crystal at 298 K. (B) A simulated spectrum (black) based on DFT calculations at the B3LYP/6-31G* level. (C) A simulated spectrum (blue) based on DFT calculations at the M06-2X/6-31G* level. Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 4 Data Obtained from X-Ray Analyses of 10a–10c (A–I) X-ray structures (front, side, and top views) of mol-1 (A–C), mol-2 (D–F), and mol-3 (G–I) in three crystallographically independent molecules of 10a at 200 K. Thermal ellipsoids are shown at the 50% probability level. (J–L) Front (J), side (K), and top (L) views of the X-ray structures of 10b at 200 K. Thermal ellipsoids are shown at the 50% probability level. (M–O) Front (M), side (N), and top (O) views of the X-ray structures of 10c at 200 K. Thermal ellipsoids are shown at the 50% probability level. (P–R) Front (P), side (Q), and top (R) views of the X-ray structures of 10c at 400 K. Thermal ellipsoids are shown at the 50% probability level. (S) Torsion angles α and d1 values of X-ray structures for 10a–10c. Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 5 D Maps of 10c (A) Difference electron density map (D map) around the ultralong C1–C2 bond in 10c at 200 K. The contour interval is 0.05 eA−3: solid lines are positive values (green), and dotted lines are zero (blue) and negative values (red). (B) D map around the ultralong C1–C2 bond in 10c at 400 K. The contour interval is 0.05 eA−3: solid lines are positive values (green), and dotted lines are zero (blue) and negative values (red). Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions

Figure 6 1H NMR Spectra of 10c with an Ultralong C1–C2 Bond (A) Spectrum of 10c in CDCl3 at 296 K after the solution was allowed to stand at ambient temperature for 100 days under air. (B) Spectrum of 10c in CDCl3 at 296 K before standing. Peaks were assigned with the support of the two-dimensional 1H-1H correlation spectroscopy NMR spectrum and the presence of nuclear Overhauser effects between HA/Hc, HD/HE, and Ha/Hb. The residual proton signal of the solvent (CHCl3, δ = 7.26 ppm) is marked with an asterisk. Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions

Scheme 1 Preparation of Dispiro(dibenzocycloheptatriene) Derivatives Chem 2018 4, 795-806DOI: (10.1016/j.chempr.2018.01.011) Copyright © 2018 Elsevier Inc. Terms and Conditions