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Volumn 6, Issue 5, 2015, Pages 2746-2753

Theoretical studies on a carbonaceous molecular bearing: Association thermodynamics and dual-mode rolling dynamics

Author keywords

[No Author keywords available]

Indexed keywords

DYNAMICS; FULLERENES; MOLECULES; THERMODYNAMICS; VAN DER WAALS FORCES;

EID: 84928138258     PISSN: 20416520     EISSN: 20416539     Source Type: Journal    
DOI: 10.1039/c5sc00335k     Document Type: Article
Times cited : (48)

References (85)
  • 3
    • 0036680315 scopus 로고    scopus 로고
    • M. Monthioux Carbon 2002 40 1809 1823
    • (2002) Carbon , vol.40 , pp. 1809-1823
    • Monthioux, M.1
  • 5
    • 84928120637 scopus 로고    scopus 로고
    • note
    • Adopting a technological term used by bearing engineers (cf. ref. 50), we describe the dynamic motions of fullerene journals as "rolling". This description also helps to avoid the confusion with the other dynamics of arylene units or alkyl substituents that have freedom of "rotations".
  • 15
    • 84928120636 scopus 로고    scopus 로고
    • http://www.orgchem2.chem.tohoku.ac.jp/finite/
  • 27
    • 84928120635 scopus 로고    scopus 로고
    • note
    • Structure-thermodynamics studies indicated that the contribution of alkyl chains on the thermodynamics is not large for [4]CC. See ref. 6b.
  • 46
    • 84928120634 scopus 로고    scopus 로고
    • note
    • In solution, the pyrrolidine ring on the fullerene molecule acts as a shaft for the single-axis rolling motion of the journal, and, in the time-averaged structure, this five-membered ring stands aligned along the C4 symmetry axis of the outer [4]CC bearing.
  • 49
    • 84928120633 scopus 로고    scopus 로고
    • note
    • Note that ITC analysis directly provides an experimental enthalpy for the association, which enables straightforward comparisons with theoretical energetics without nuisance considerations of entropic terms (see also ref. 48 and 49).
  • 50
    • 84928120632 scopus 로고    scopus 로고
    • note
    • The association enthalpy of unsubstituted C60 in dichloromethane is -11.6 ± 0.4 kcal mol-1 (ref. 5 and 6d), which shows that introduction of substituents does not hinder but rather enforces the association of the journal by ca. -1 kcal mol-1
  • 51
    • 84928120631 scopus 로고    scopus 로고
    • note
    • The dispersion force is undoubtedly playing a key role for the peapod formation with close van der Waals contacts (ref. 6b), and the present results indicate its premature treatment in the present DFT methods (see also ref. 34). Effects on the lengthening of the tubular structure is thus of great interest for in the near future. (See also ref. 6d).
  • 52
    • 84928120630 scopus 로고    scopus 로고
    • note
    • The geometries from LC-BLYP/PCM and BMK/PCM methods matched with RMSD of 0.090 Å. See Fig. S1
  • 55
    • 84928120629 scopus 로고    scopus 로고
    • note
    • Yamago and coworkers also reported a tendency of overestimate of association energies with M06-2X. See ref. 8.
  • 56
    • 84928120628 scopus 로고    scopus 로고
    • note
    • One reviewer expressed his/her interest in further extensions of polarization functions over hydrogen atoms as well as in other DFT methods with more recent dispersion treatments. Albeit preliminary within a framework of the Gaussian program, these comparisons were made by single-point calculations, and the results were summarized in Table S1. In short, the extension of polarization functions to (d,p) setting did not affect the results considerably. The inclusion of dispersion effects with modern D3 methods did not improve the results by showing overestimations of the association energy over 35 kcal mol-1. The results may indicate that further improvements in the theoretical models of dispersion forces are necessary especially for the curved π-systems. The present results also show that our carbonaceous molecular bearing provides an interesting and challenging test case for theoretical evaluations (ref. 48d), and the evaluation of other recent dispersion models, such as many-body dispersion models implemented in the Amsterdam Density Functional program, may be of interest for the further theoretical studies in the future. See ref. 48 for representative examples.
  • 58
    • 84928120626 scopus 로고    scopus 로고
    • note
    • The rolling energetics also shows that the starting geometry is the global minimum for the single-axis rolling motions by showing the minimum at 0° in Fig. 3.
  • 60
    • 84928120625 scopus 로고    scopus 로고
    • note
    • The two carbon atoms on the equator are located in the middle of biaryl linkages. A similar anomalous location of carbon atoms on the biaryl linkages is also experimentally observed in the solid state. See ref. 6b.
  • 64
    • 84928120624 scopus 로고    scopus 로고
    • note
    • The association energy of (P)-(12,8)-[4]CC⊃ 1+ was estimated as -78.9 kcal mol-1 by the DFTB method. This value was larger than that of ωB97X-D method (-69.8 kcal mol-1, cf. Table 1).
  • 65
    • 84928120623 scopus 로고    scopus 로고
    • note
    • PCM implementation in the DFTB method is not accessible with our resource using DFTB+ program (cf. ref. 52).
  • 66
    • 84928120622 scopus 로고    scopus 로고
    • note
    • Although the relative stabilities of two minima were switched from the LC-BLYP calculations, the energy differences of minima were as small as <0.2 kcal mol-1 for SCC-DFTB calculations and <0.6 kcal mol-1 for LC-BLYP calculations. The switching of two minima may be the origin of minimum-switching of realistic motions (Fig. S5): stabilities of 1/4 precession and bp structures were switched between SCC-DFTB and LC-BLYP calculations.
  • 67
    • 84928120621 scopus 로고    scopus 로고
    • note
    • Because of minute differences in the chemical shifts of resonances, we could not study the experimental dynamics of this system
  • 73
    • 84928120620 scopus 로고    scopus 로고
    • note
    • The energy barriers from MD and TS analysis are comparable to the one estimated with LC-BLYP/PCM for the idealized rolling motions (Fig. S4, +4.3 kcal mol-1).
  • 81
    • 84928120619 scopus 로고    scopus 로고
    • note
    • Delicate care must be taken in the comparison of experimental and theoretical data especially for large supramolecular systems. As we experimentally demonstrated in our systems (ref. 6), entropy terms in the association should be very complicated by the involvement of conformations and solvent molecules. Such entropy effects cannot be readily reproduced by any simple theoretical models (ref. 48).
  • 84
    • 84928120618 scopus 로고    scopus 로고
    • Bremen Center for Computational Materials Science, University of Bremen. See also
    • Bremen Center for Computational Materials Science, University of Bremen. See also http://www.dftb-plus.info


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.