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Adsorption of Carbon Tetrahalides on Coronene and Graphene Miran Ha, Dong Yeon Kim, Nannan Li, Jenica Marie L. Madridejos, In Kee Park, Il-Seung Youn, Joonho Lee, Chunggi Baig, Michael Filatov, Seung Kyu Min, Geunsik Lee, and Kwang S. Kim J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b04939 • Publication Date (Web): 16 Jun 2017 Downloaded from http://pubs.acs.org on June 18, 2017

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The Journal of Physical Chemistry

Adsorption of Carbon Tetrahalides on Coronene and Graphene Miran Ha,‡,b Dong Yeon Kim,‡,b Nannan Li,a Jenica Marie L. Madridejos,a In Kee Park,a Il Seung Youn,a Joonho Lee,c Chunggi Baig,b Michael Filatov,a Seung Kyu Min,*,a Geunsik Lee,*,a and Kwang S. Kim*,a RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to) *Corresponding authors: [email protected] (gl), [email protected] (skm), or [email protected] (ksk) ‡ These authors contributed equally to this work. a Department of Chemistry, bDepartment of Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 44919, Korea c Department of Chemistry, University of California, Berkeley, CA 94720-1460, USA ABSTRACT Since carbon tetrahalides CX4 (X=Cl/Br) can be well adsorbed on carbon nanotubes and graphene sheets, we have studied the structures, adsorption energies, and electronic properties of CX4 adsorbed on benzene, coronene, and graphene using dispersion corrected density functional theory (DFT) with hybrid functionals. As compared with the benzene–CX4 complexes (with binding energy of ~14/15 kJ/mol) where electrostatic energy is significant due to the halogen bonding effect, the graphene–CX4 complexes show about three times the benzene–CX4 binding energy (~40/45 kJ/mol) where the dispersion interaction is overwhelming with insignificant electrostatic energy. Since the X atoms in CX4 are slightly positively charged and the X atom’s ends are particularly more positively charged due to the σ-hole effect, CX4 behaves as an electron acceptor. This results in electron transfer from locally negatively charged C sites of benzene/coronene to CX4. In contrast, no electron transfer occurs from graphene to CX4 because of large work function of graphene and significant electron affinity of CX4 and because homogenously charge-neutral graphene has no locally charged sites. Nevertheless, due to the symmetry breaking upon adsorption, the CX4-adsorbed graphene shows a small band gap opening without p-doping. On the other hand, CF4 behaves as an electron donor due to the negatively charged F atoms, which results in electron transfer from CF4 to the locally negatively charged C sites of benzene/coronene. Again, no electron transfer occurs from CF4 to graphene because of high ionization energy of CF4, and so the CF4-adsorbed graphene opens only a small band gap without n-doping. 1

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INTRODUCTION Since the advent of graphene (Gr), 2-dimensional chemistry has emerged with functionalization of Gr,1 noncovalent adsorption on Gr,2-6 and intercalation inside Gr–bilayer.711

For example, ferric chloride (FeCl3)n intercalated between graphene bi-layers shows

intriguing Shubnikov de Haas oscillations in magnetoresistance,7 and alkali and alkali-earth metal intercalated between graphene bi-layers are found to be superconducting.8-11 Carbon tetrahalides CX4 (X=Cl/Br) can be adsorbed on carbon nanotubes12 and Gr sheets.13 On the basis of the electronegativity values of C, I, Br, Cl, F (2.55, 2.66, 2.96, 3.16, 3.98 respectively),14 each halogen atom linked to C could be expected to be negatively charged. However, when the central C atom is bonded tetrahedrally to four atoms of Cl/Br/I (excluding F which is strongly electronegative), each halide atom loses a small portion of electron population via C atom due to three remaining electron withdrawing halogen atoms on the opposite sides; then, each halogen atom (excluding F) eventually becomes slightly positively charged. Furthermore, tips of the X atoms show more positive electrostatic potential due to the anisotropic charge distribution in the σ-hole which causes halogen bonding. In this situation, it is interesting to find out how CX4 binds to Gr and whether the CX4 adsorbed on Gr can behave as an electron acceptor/donor, thus generating p/n-type charge carriers in Gr. Here, we investigate the geometry and binding energy of CX4 adsorbed on coronene (Cor) and Gr using DFT with dispersion correction. Complexation of halides with extended π systems may involve several competing noncovalent interactions, such as dispersion interaction, halogen bonding,15–33 and hydrogen bonding. Due to relatively deficient electron density, the σ-hole17,18 lying on the axis of a halogen bond is partially positively charged. Hence, it undergoes attractive interaction with electron rich sites, and so the electrostatic interaction is expected to be a major component of halogen bonding.16–18 However, the dispersion interaction can make a significant contribution34–37 to bonding in π–X complexes, thus redefining the possible conformations of these systems. Since Cor and Gr are large π systems, their complexation with CX4 can strongly depend on the π–X interactions. Recently, we investigated π−X interactions in benzene (Bz) using Bz−CX4 complexes with a variety of ab initio and DFT methods.38 Most of the DFT methods (in particular, the D3 dispersion-corrected39 generalized gradient approximations (GGAs)) seriously overestimate the energies involved in strong halogen bonding, as compared 2


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with the complete basis set (CBS) limit of coupled-cluster with single, double, and non-iterative triple excitations [CCSD(T)]. The overestimation is caused by delocalization error of the GGA density functionals and it can be reduced by using hybrid functionals. Accurate description of highly anisotropic electron density around the halogen bond requires the use of large basis sets because such anisotropic effects are not adequately described with small basis sets. We also note that the basis-set-superposition-error (BSSE) uncorrected M06-2X40 functional with the aug-cc-pVTZ (aVTZ) basis set performs well for Bz–X2, however the CBS values are underestimated.39 For periodic systems, PBE-TS (based on Tkatchenko–Scheffler empirical dispersion correction41) and PBE42-D3 perform reasonably well for all cases except strong halogen bonding. Improved description of the latter requires the use of hybrid PBE043-D3 or PBE0-TS functionals. As the latter functionals provide improved description of halogen bonding, they are used in this work to model the Cor and Gr systems.

COMPUTATIONAL DETAILS The ability of the density functionals used in this work to reproduce the reference CCSD(T)/CBS values was evaluated with the calculation of binding energies of the Bz−CX4 complexes. The DFT CBS values were estimated by pseudo interpolation between the BSSE corrected and uncorrected energies44–46 obtained using the aug-cc-pVNZ basis sets (denoted aVNZ in the following) with N = T, Q for Bz−CX4 and N = D, T for Cor−CX4. As the number of possible conformations of the CX4 complexes with Cor and Gr can be sufficiently large, the relevant local minima were first identified using relatively cheap B9747,48-D3/aVDZ geometry optimizations. The local/global minima were confirmed by the analysis of vibrational frequencies. The obtained conformations were used as the starting geometries for the calculations employing the M06-2X, PBE-D3, and PBE-TS functionals. For Bz–CX4 and Cor–CX4 systems, PBE0-D3/CBS and PBE0-TS/tier3 calculations were carried out to obtain more reliable binding energies, where tier is used as light-tier. For the above systems, the calculations using periodic boundary condition were additionally performed with the PBE0/PW and the vdw-DF2/PW (with rPW86)49 functionals using the plane wave (PW) basis to enable direct comparison with the Gr–CX4 system. For the Gr–CX4 system, the PBED3/PW, PBE-TS/PW, PBE-TS/tier3, PBE-TS/tier2, PBE0-D3/PW, PBE0-TS/PW, PBE0TS/tier2, and vdW-DF2/PW calculations were performed. 3



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The calculations were performed using the program packages of Turbomole,50 Fritz Haber Institute ab initio molecular simulations (FHI-AIMS),51 Vienna Ab-initio Simulation Package (VASP),52 Molpro,53 and Gaussian09.54 Since VASP inherently imposes periodic boundary conditions, the size of cells was chosen to be large enough to neglect the influence of the nearest cells (for example, 12 Å vacuum region inserted for the cluster type, 12.78 Å × 12.78 Å × 20 Å in PBE calculations (9.84 Å × 9.84 Å × 20 Å in PBE0 calculations) for Gr. The projected augmented wave (PAW) pseudopotentials for the electron-ion interactions and the cutoff energy 500 eV for the PW basis set were used,55,56 and a Monkhorst-Pack grid of 5×5×1 k-points were employed for Gr in PBE calculation (3×3×1 k-points in PBE0 calculation; Table S1), while only Gamma point for the cluster. In the case of Gr-complexes, the relaxation of the Gr sheet was not significant.57 Hence, the geometry of Gr sheet was kept frozen (e.g., assuming that the Gr sheet is on the surface of a substrate) and only the geometry of each adsorbed molecule was optimized. The natural bonding orbital (NBO)58 calculations were performed using NBO program as implemented in the Gaussian09 to analyze partial charge of C atoms of Bz, Cor, and CX4 atoms (X=F, Cl, and Br).

RESULTS AND DISCUSSION Before starting calculations for the Gr–CX4 system, the ability of the density functionals used in this work is tested by investigating whether the CCSD(T)/CBS values of the binding energy in the StagC (Figure 1a) and Side (Figure 1b) conformations of Bz–CX4 complexes are adequately reproduced. Table 1 shows the computed binding energies where the energies within 1 kJ/mol from the CCSD(T)/CBS target values are highlighted. The M06X2X/aVTZ method yields binding energies in good agreement with the CCSD(T)/CBS values, whereas the M06-2X/CBS method underestimates them. The PBE0 binding energies are generally in better agreement with the reference values (deviations of 1.1/0.3 kJ/mol for StagC Bz–CCl4/CBr4 and 1.0/0.8 kJ/mol for Side Bz–CCl4/CBr4) than the PBE energies (deviations of 1.2/0.7 kJ/mol for StagC and 1.5/1.1 kJ/mol for Side). It is noteworthy that the C atoms in the Bz ring are negatively charged as evidenced by their NBO charges (QC) of −0.236 a.u. at the PBE0-D3/aVDZ level. The energies of π–X interactions in the Cor–CCl4/CBr4 complexes were calculated 4


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using the same density functionals as for the Bz–CX4 adducts. Cor differs from Bz in that the charges are not uniformly distributed across its carbon atoms; hence, one can expect certain differences between the Bz–CX4 and Cor–CX4 complexes. For example, the C atoms in the aromatic ring located near the center of Cor are almost electrically neutral (QC = -0.012 a.u. at the PBE0–D3/aVDZ level), while the C atoms on the edge of Cor ring are more negative (QC = -0.206 a.u.). For the Cor–CCl4/CBr4 complexes, a large set of initial conformations was generated, however the geometry optimizations converged to four stable conformers shown in Figure 2 and Table 2. The most stable two nearly isoenergetic conformers [Stagg: staggered tripod on the ring center (Figure 2a), Eclip: eclipsed tripod on the ring center (Figure 2b)] feature three halogen atoms facing the Cor plane and interacting with the highly delocalized π–electron cloud of the Cor ring. Overall, the Stagg structure is a fraction of kJ/mol more stable than the Eclip structure and a few kJ/mol more stable than the Edge structure (Figure 2c), and it is ~20 kJ/mol more stable than the Side structure (Figure 2d). The latter conformation is stabilized by weak halogen bonding alone and it lacks stabilization due to dispersion. To evaluate the relative contribution of the dispersion and electrostatic interactions to the overall stabilization energy of Bz–CX4, we carried out energy decomposition analysis using symmetry adapted perturbation theory (SAPT),59,60 see Table 3. The DFT-SAPT energy decomposition was carried out using the aVDZ basis set and the asymptotically corrected PBE0 (PBE0AC) exchange-correlation (xc) functional, where adiabatic local density approximation (ALDA)61 xc kernel was used to calculate the induction and dispersion components and their exchange counterparts. In the DFT-SAPT calculations, the BSSE-corrected MP2/aVDZ geometry of the StagC conformation of Bz–CCl4/CBr4 was used; this is the most stable conformation of these complexes. The StagC conformers of Bz–CX4 show strong dispersion energy (–24/–23 kJ/mol for Cl/Br) and substantial electrostatic energy (–10/–9 kJ/mol). We note that QC = −0.236 a.u. in Bz and QC = −0.012 a.u. in Cor at the PBE0–D3/aVDZ level. As QC is smaller in Cor than in Bz, it is expected that the electrostatic contribution is reduced in Cor. It is also expected that the electrostatic contribution to the interaction energy should be eventually negligible in Gr since the C atoms in Gr are electrically neutral due to the high conductivity of metallic Gr. As shown in Figure 3 and Table 4, the Gr–CX4 system has the global minimum at the 5



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StagC geometry (Figure 3a: staggered tripodal conformation with the central C atom of CX4 located just above the graphene C atom), which is 2–3 kJ/mol more stable than the Eclip structure (Figure 3b: eclipsed tripodal conformation around the hexagon centroid). The Leg1C conformation with one X pod on a graphene C atom (Figure 3c) is much less stable. We find that despite being stabilized predominantly by dispersion interaction, the Gr–CX4 complexes have ~3 times stronger binding energies (~35–42/~38–47 kJ/mol) than the Bz–CX4 complexes (13.6/15.0 kJ/mol). The Gr–CBr4 systems have ~5 kJ/mol stronger binding energy than the GrCCl4 systems due to larger dispersion interaction with Br, which has a larger number of electrons than Cl. It is of note that the PBE0-D3 binding energies of Gr–CX4 (which might not properly take into account the dispersed electron clouds with metallic behavior of Gr) are somewhat smaller than the PBE0–TS values, by contrast to the Bz–CX4 and Cor–CX4 systems where both PBE0-D3 and PBE0-TS yield almost the same binding energies. As Gr is highly conductive, charge accumulation on the Gr surface is negligible, which results in an insignificant electrostatic component of the interaction energy but a more substantial dispersion energy component due to almost uniformly dispersed nature of electron clouds. The X atoms in CX4 are slightly positively charged; the NBO charge of Cl/Br (QCl/Br) is 0.071/0.157 a.u. (positive value) at the PBE0-D3/aVDZ level. By contrast, the NBO atomic charge of F (QF) in CF4 is –0.364 a.u. (negative value). At the CCSD/aVDZ level, QCl/Br = 0.067/0.159 a.u. and QF = –0.367 a.u. (Figure 4a). For CF4, CCl4, and CBr4, the ionization energies are 16.2, 11.5, and 10.3 eV, respectively,62 and the electron affinities are -1.2 (or 0), 0.80-2.00, and 2.06 eV, respectively.63 Owing to the positive electron affinities, CCl4 and CBr4 behave as an electron acceptor, while owing to the negative (or zero vertical) electron affinity, CF4 behaves as an electron donor. Thus, these affinity values are in agreement with the positive QCl/Br and negative QF. Since the tip of X atom has a somewhat more positive electrostatic potential due to the anisotropic character of the σ-hole charge distribution, one could expect that CX4 in Cor and Gr complexes behaves as an electron acceptor. Indeed, CCl4/CBr4 behaves as an electron acceptor in its C96H24 complex (see the electron transfer in Figure 4a). However, undoped graphene has large work function (~4.6 eV),64 and so the electron transfer cannot easily occur from graphene to CX4. We investigated the electron transfer from/to the CX4 (X = Cl/Br) molecules adsorbed on Cor, C54H18, and C96H24 also. The electron transfer from CCl4/CBr4 to the π-complex decreases (eventually to zero) as the size of π system increases 6


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(Figures 4). Then, it is expected that the role of CX4 in acting as an electron acceptor with respect to graphene will disappear. In contrast, CF4 with the negatively charged F atoms behaves as an electron donor in its C96H24 complex. The amount of electron transfer from CF4 to the π system increases (up to 0.0066 a.u.) with increasing size of π system, which could play the role as an electron donor (Figure 4b). Nevertheless, CF4 does not play the role in acting as an electron donor on graphene due to the high ionization energy of CF4 (16.2 eV). The effect of CX4 adsorption on the graphene electronic band structure is calculated at the PBE-D3/PW level. As shown in Figure 5a, the pristine graphene shows the Dirac dispersion with the zero band gap. However, with CX4 adsorption in StagC geometry, as shown in Figures 5b−5d, the band gap opens by 1.7 meV for X = F and 3.6 meV for X = Cl, Br. This small gap opening and almost intact linear dispersion are caused by weakly adsorbed CX4 which breaks the symmetry of two sublattice onsite energies. It is worth noting previous works that X2 and aromatic molecules adsorbed on graphene open small band gaps.65,66

CONCLUDING REMARKS We carried out first principles calculations of the π–CX4 (X = Cl/Br) and π–CF4 systems, where π stands for Bz, Cor, and Gr. The relative magnitude of the dispersion interaction and the electrostatic interaction contributions to the overall binding energy of the Bz–CX4 complexes was evaluated based on the DFT-SAPT analysis. Compared to Bz–CX4 with the binding energies in the range of 13~15 kJ/mol, the binding energy of Cor–CX4 increases more than twice to ~30/34 kJ/mol, and it is tripled in the Gr–CX4 complexes where it reaches ~42/47 kJ/mol. Analysis of the NBO charges on C atoms in Bz, Cor, and Gr suggests that the electrostatic contribution to the interaction energy in Gr–CX4 complexes is greatly reduced compared to the Bz–CX4 complexes due to almost perfect charge-neutral carbon atoms in the former. Hence, the Gr–CX4 complexes are stabilized predominantly by the dispersion interaction, whereas in the Bz–CX4 complexes both dispersion and electrostatic interactions contribute to the final binding energy. Since Br has more electrons than Cl, the Gr–CBr4 complex has slightly stronger binding energy than the Gr–CCl4 complex due to stronger dispersion interaction of graphene. CX4 behaves as an electron acceptor, withdrawing electrons from Cor, but there is no electron transfer from graphene to CX4 because of significant positive electron affinity of CX4 and large work function of graphene. Nevertheless, CX4-adsorbed 7



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graphene have small band gap opening due to the symmetry breaking upon adsorption. In contrast, CF4 with negatively charged F atoms behaves as an electron donor for Bz/Cor. However, CF4 does not act as an electron donor on graphene because of the high ionization energy of CF4. We believe that the analysis of π–X interactions in large π–systems should be useful

in

the

studies

of

halogen-adsorption/intercalation

for

graphene/graphite

functionalization with halogen-containing molecules.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc. Difference in binding energies for different sizes of k points (Table S1). AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (gl), [email protected] (skm), or [email protected] (ksk) ORCID Kwang S. Kim: http://orcid.org/0000-0002-6929-5359 Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS The financial support from NRF (National Honor Scientist Program: 2010-0020414) and UNIST (1.140111.01) is greatly acknowledged. KISTI (KSC-2016-C3-0074, KSC-2015-C1010) has provided supercomputing time.

REFERENCES (1)

Georgakilas, V.; Otyepka, M.; Bourlinos, A. B.; Chandra, V.; Kim, N.; Kemp, K. C.; Hobza, P.; Zboril, R.; Kim, K. S. Functionalization of Graphene: Covalent and 8


Page 9 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Noncovalent Approaches, Derivatives and Applications, Chem. Rev. 2012, 112, 61566214. (2)

Kong, L.; Enders, A.; Rahman, T. S.; Dowben, P. A. Molecular Adsorption on Graphene. J. Phys.: Condens. Matter 2014, 26, 443001.

(3)

Yang, J, W.; Lee, G.; Kim, J. S.; Kim, K. S. Gap Opening of Graphene by Dual FeCl3Acceptor and K-Donor Doping, J. Phys. Chem. Lett. 2011, 2, 2577-2581.

(4)

Şahin, H.; Ciraci, S. J. Chlorine Adsorption on Graphene: Chlorographene, J. Phys. Chem. C, 2012, 116, 24075-24083.

(5)

Xu, C.; Brown, P. A.; Lu, J.; Shuford, K. L. Electronic Properties of Halogen-Adsorbed Graphene, J. Phys. Chem. C, 2015, 119, 17271-17277.

(6)

Jung, N.; Crowther, A.; Kim, N.; Kim, P.; Brus, L. Raman Enhancement on Graphene: Adsorbed and Intercalated Molecular Species, ACS Nano 2010, 4, 7005-7013.

(7)

Kim, N.; Kim, K. S.; Jung, N.; Brus, L.; Kim, P. Synthesis and Electrical Characterization of Magnetic Bilayer Graphene Intercalate, Nano Lett. 2011, 11, 860-865.

(8)

Ichinokura, S.; Sugawara, K.; Takayama, A.; Takahashi, T.; Hasegawa, S. Superconducting Calcium-Intercalated Bilayer Graphene. ACS Nano 2016, 10, 2761– 2765.

(9)

Ludbrook, B. M.; Levy, G.; Nigge, P.; Zonno, M.; Schneider, M.; Dvorak, D. J.; Veenstra, C. N.; Zhdanovich, S.; Wong, D.; Dosanjh, P.; et al. Evidence for Superconductivity in Li-Decorated Monolayer Graphene. Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 11795– 11799.

(10) Profeta, G.; Calandra, M.; Mauri, F. Phonon-Mediated Superconductivity in Graphene

by Lithium Deposition. Nat. Phys. 2012, 8, 131–134. (11) Rahnejat, K. C.; Howard, C. A.; Shuttleworth, N. E.; Schofield, S. R.; Iwaya, K.;

Hirjibehedin, C. F.; Renner, C.; Aeppli, G.; Ellerby, M. Charge Density Waves in the Graphene Sheets of the Superconductor CaC6. Nat. Commun. 2011, 2, 558. (12) Babaa, M. R.; Dupont-Pavlovsky, N.; McRae, E.; Masenelli-Varlot, K. Physical

Adsorption of Carbon Tetrachloride on As-produced and on Mechanically Opened Single Walled Carbon Nanotubes, Carbon 2004, 42, 1549-1554. (13) Bermudez, V. M.; Robinson, J. T. Effects of Molecular Adsorption on the Electronic

Structure of Single-Layer Graphene. Langmuir 2011, 27, 11026-11036. 9



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 25

(14) Allred, A. L. Electronegativity Values from Thermochemical Data. J. Inorg. Nucl. Chem.1961, 17, 215-221. (15) Cavallo, G.; Metrangolo, P.; Milani, R.; Pilati, T.; Priimagi, A.; Resnati, G.; Terraneo, G. The Halogen Bond, Chem. Rev. 2016, 116, 2478-2601 (16) Riley, K. E.; Hobza, P. Investigations into the Nature of Halogen Bonding Including Symmetry Adapted Perturbation Theory Analyses, J. Chem. Theory Comput. 2008, 4, 232-242. (17) Politzer, P.; Murray, J, S.; Clark, T. Halogen Bonding: an Electrostatically-Driven Highly Directional Noncovalent Interaction, Phys. Chem. Chem. Phys. 2010, 12, 7748-7757. (18) Politzer, P.; Murray, J, S.; Clark, T. Halogen Bonding and Other σ-hole Interactions: a Perspective, Phys. Chem. Chem. Phys. 2013. 15, 11178-11189. (19) Sedlak, R.; Kolar, M. H.; Hobza, P. Polar Flattening and the Strength of Halogen Bonding, J. Chem. Theory Comput. 2015, 11, 4727-4732. (20) Fanfrlik, J.; Ruiz, F. X.; Kadlcikova, A.; Rezac, J.; Cousido-Siah, A.; Mitschler, A.; Haldar, S.; Lepsik, M.; Kolar, M. H.; Majer, P.; et al. The Effect of Halogen-to-Hydrogen Bond Substitution on Human Aldose Reductase Inhibition, ACS Chem. Biol. 2015, 10, 1637-1642. (21) Riley, K. E.; Hobza, P. Noncovalent Interactions in Biochemistry, Wiley Interdiscip. Rev. Comput. Mol. Sci. 2011, 1, 3-17. (22) Jacobsson, T. J.; Pazoki, M.; Hagfeldt, A.; Edvinsson, T. Goldschmidt’s Rules and Strontium Replacement in Lead Halogen Perovskite Solar Cells: Theory and Preliminary Experiments on CH3NH3SrI3, J. Phys. Chem. C 2015, 119, 25673-25683. (23) Kawai, S.; Sadeghi, A.; Xu, F.; Peng, L.; Orita, A.; Otera, J.; Goedecker, S.; Meyer, E. Extended Halogen Bonding between Fully Fluorinated Aromatic Molecules, ACS Nano 2015, 9, 2574-2583. (24) Forni, A.; Pieraccini, S.; Rendine, S.; Gabas, F.; Sironi, M. Halogen-Bonding Interactions with π Systems: CCSD(T), MP2, and DFT Calculations. ChemPhysChem 2012, 13, 4224-4234. (25) Kozuch, S.; Martin, J. M. L. Halogen Bonds: Benchmarks and Theoretical Analysis. J. Chem. Theory Comput. 2013, 9, 1918-1931. (26) Primagi, A.; Cavallo, G.; Metrangolo, P.; Resnati, G. The Halogen Bond in the Design of 10


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Functional Supramolecular Materials: Recent Advances. Acc. Chem. Res. 2013, 11, 26852695. (27) Forni, A.; Pieraccini, S.; Rendine, S.; Sironi, M. Halogen Bonds with Benzene: An Assessment of DFT Functionals. J. Comput. Chem. 2014, 35, 386-394. (28) Setiawan, D.; Kraka, E.; Cremer, D. Strength of the Pnicogen Bond in Complexes Involving Group Va Elements N, P, and As. J. Phys. Chem. A 2015, 119, 1642-1656. (29) Ramesh, N.; Patnaik, A. Iso-Oriented Fluorescent Colloidal Nanocrystals of BisCyanostyryl Thiophenes: Crucial SecondaryHalogen Interactions toward Stability and Transport, J. Phys. Chem. C 2016, 120, 1909-1917. (30) Liu, Z.-X.; Sun, Y.; Feng, Y.; Chen, H.; Hea, Y.-M.; Fana, Q.-H. Halogen-Bonding for Visual Chloride Ion Sensing: A Case Study Using Supramolecular Poly(aryl ether) Dendritic Organogel Systems. Chem. Comm. 2016, 52, 2269-2272. (31) Tsuzuki, S.; Uchimaru, T.; Wakisaka, A.; Ono, T. Magnitude and Directionality of Halogen Bond of Benzene with C6F5X, C6H5X, and CF3X (X = I, Br, CI, and F). J. Phys. Chem. A 2016, 120, 7020-7029. (32) Kim, D. Y.; Madridejos, J. M. L.; Ha, M.; Kim, J.-H.; Yang, D. C.; Baig C.; Kim, K. S. Size-Dependent Conformational Change in Halogen–π Interaction: from Benzene to Graphene. Chem. Comm. 2017, 53, 6140-6143. (33) B4H4 and B4(CH3)4 as Unique Electron Donors in Hydrogen-Bonded and HalogenBonded Complexes. J. Phys. Chem. A 2016, 120, 5745-5751. (34) Bauza, A.; Alkorta, I.; Frontera, A.; Elguero, J. On the Reliability of Pure and Hybrid DFT Methods for the Evaluation of Halogen, Chalcogen, and Pnicogen Bonds Involving Anionic and Neutral Electron Donors, J. Chem. Theory Comput. 2013, 9, 5201-5210. (35) Matter, H.; Nazaré, M.; Güssregen, S.; Will, D, W.; Schreuder, H.; Bauer, A.; Urmann, M.; Ritter, K.; Wagner, M.; Wehner, V. Evidence for C-Cl/C-Br···π Interactions as an Important Contribution to Protein–Ligand Binding Affinity, Angew. Chem. Int. Ed. 2009, 48, 2911-2916. (36) Ran, J.; Hobza, P. On the Nature of Bonding in Lone Pair···π-Electron Complexes: CCSD(T)/Complete Basis Set Limit Calculations, J. Chem. Theory Comput. 2009, 5, 1180-1185. (37) Noman, A.; Rahman, M. M.; Bishop, R.; Craig, D. C.; Scudder, M. L. Analysis of π– 11



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halogen dimer interactions present in a family of staircase inclusion compounds. CrystEngComm 2003, 5, 422-428. (38) Youn, I. S.; Kim, D. Y.; Cho, W. J.; Madridejos, J. M. L.; Lee, H. M.; Kolaski, M.; Lee, J.; Baig, C.; Shin, S. K,; Filatov, M.; et al. Halogen−π Interactions between Benzene and X2/CX4 (X = Cl, Br): Assessment of Various Density Functionals with Respect to CCSD(T), J. Phys. Chem. A 2016, 120, 9305-9314. (39) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. A Consistent and Accurate Ab Initio Parametrization of Density Functional Dispersion Correction (DFT-D) for the 94 Elements H-Pu, J. Chem. Phys. 2010, 132, 154104. (40) Zhao, Y.; Truhlar, D. G. The M06 Suite of Density Functionals for Main Group Thermochemistry, Thermochemical Kinetics, Noncovalent Interactions, Excited States, and Transition Elements: Two New Functionals and Systematic Testing of Four M06Class Functionals and 12 Other Functionals,Theor. Chem. Acc. 2008, 120, 215-241. (41) Tkatchenko, A.; Scheffler, M. Accurate Molecular Van Der Waals Interactions from Ground-State Electron Density and Free-Atom Reference Data, Phys. Rev. Lett. 2009, 102, 073005. (42) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple, Phys. Rev. Lett. 1996, 77, 3865-3868. (43) Adamo, C.; Barone, V. Toward Reliable Density Functional Methods Without Adjustable Parameters: The PBE0 Model. J. Chem. Phys. 1999, 110, 6158−6170. (44) Shin, I.; Park, M.; Min, S. K.; Lee, E. C.; Suh, S. B.; Kim, K. S. Structure and Spectral Features of H+(H2O)7 : Eigen versus Zundel Forms, J. Chem. Phys. 2006, 125, 234305. (45) Lee, E. C.; Kim, D.; Jurečka, P.; Tarakeshwar, P.; Hobza, P.; Kim, K. S. Understanding of Assembly Phenomena by Aromatic−Aromatic Interactions: Benzene Dimer and the Substituted Systems, J. Phys. Chem. A 2007, 111, 3446-3457. (46) Min, S. K.; Lee, E. C.; Lee, H. M.; Kim, D. Y.; Kim, D.; Kim, K. S. Complete Basis Set Limit of Ab Initio Binding Energies and Geometrical Parameters for Various Typical Types of Complexes, J. Comp. Chem. 2008, 29, 1208-1221. (47) Becke, A. D. Density-Functional Thermochemistry. V. Systematic Optimization of Exchange correlation Functionals, J. Chem. Phys. 1997, 107, 8554-8560. (48) Schmider, H. L.; Becke, A. D. Optimized Density Functionals from the Extended G2 Test 12


Page 13 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Set, J. Chem. Phys. 1998, 108, 9624-9631. (49) Klimeš, J.; Bowler, D. R.; Michaelides, A. Van Der Waals Density Functionals Applied to Solids, Phys. Rev. B, 2011, 83, 195131. (50) TURBOMOLE V6.4 2009, A development of University of Karlsruhe and Forschungszentrum Karlsruhe GmbH, 1989-2007, TURBOMOLE GmbH, since 2007; available from http://www.turbomole.com (51) Blum, V.; Gehrke, R.; Hanke, F.; Havu, P.; Havu, V.; Ren, X.; Reuter, K.; Scheffler, M. Compt. Ab Initio Molecular Simulations with Numeric Atom-Centered Orbitals, Phys. Commun. 2009, 180. 2175-2196. (52) Kresse, G.; Furthmüller, J. Efficient Iterative Schemes for Ab Initio Total-Energy Calculations Using a Plane-Wave Basis Set, Phys. Rev. B 1996, 54, 11169-11185. (53) Werner, H.-J.; Knowles, P. J.; Lindh, R.; Manby, F. R.; Schutz, M.; Celani, P.; Korona, T.; Rauhut, G.; Amos, R. D.; Bernhardsson, A., et al. MOLPRO, a package of ab initio programs, version 2010.1, Institut für Theoretische Chemie, Universität Stuttgart, Stuttgart, Germany, 2006. (54) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.;Petersson, G. A.; et al. Gaussian 09, Revision D.01; Gaussian, Inc.:Wallingford, CT, 2009. (55) Blöchl, P. E. Projector Augmented-Wave Method, Phys. Rev. B 1994, 50, 17953-17979. (56) Kresse, G.; Joubert, D. From Ultrasoft Pseudopotentials to the Projector AugmentedWave Method, Phys. Rev. B 1999, 59, 1758-1775. (57) Cho, Y.; Min, S. K.; Yun, J.; Kim, W. Y.; Tkatchenko, A.; Kim, K. S. Noncovalent Interactions of DNA Bases with Naphthalene and Graphene, J. Chem. Theory Comput. 2013, 9, 2090-2096. (58) Weinhold F. and Lands C. R. Natural Bond Orbitals and Extensions of Localized Bonding Concepts, Chem. Educ. Res. Pract. 2001, 2, 91–104. (59) Jeziorski, B.; Moszynski, R.; Szalewicz, K. Perturbation Theory Approach to Intermolecular Potential Energy Surfaces of Van Der Waals Complexes. Chem. Rev. 1994, 94, 1887−1930. (60) Heßelmann, A.; Jansen, G.; Schütz, M. Density-functional theory-symmetry-adapted intermolecular perturbation theory with density fitting: A new efficient method to study 13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

intermolecular interaction energies. J. Chem. Phys. 2005, 122, 014103. (61) Gross, E. K. U.; Dobson, J. F.; Petersilka, M. Density Functional Theory of TimeDependent Phenomena. Top. Curr. Chem. 1996, 181, 81. (62) Kime, Y. J.; Driscoll, D. C.; Dowben, P. A., The Stability of the Carbon Tetrahalide Ions, J. Chem. Soc. Faraday Trans. 2, 1987, 83, 403-410. (63) NIST Chemistry WebBook, http://webbook.nist.gov/chemistry/ion-ser.html, 2017. (64) Yu, Y.-J.; Zhao, Y.; Ryu, S.; Brus, L. E.; Kim, K. S.; Kim, P. Tuning the Graphene Work Function by Electric Field Effect, Nano Lett. 2009, 9, 3430-3434. (65) Chang C.-H.; Fan X.; Li L.-J.; Kuo J.-L. Band Gap Tuning of Graphene by Adsorption of Aromatic Molecules. J. Phys. Chem. C 2012, 116, 13788-13794. (66) Shayeganfar F.; Rochefort A. Electronic Properties of Self-Assembled Trimesic Acid Monolayer on Graphene. Langmuir 2014, 30, 9707-9716.

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Table 1. Binding energies (kJ/mol) of Bz–CCl4/CBr4.a StagC Side CCSD(T)/CBS 13.62/15.03 8.13/9.96 CCSD(T)/aVTZ 12.03/13.23 7.55/9.15 M06-2X/CBS 12.59/14.24 6.60/6.69 M06-2X/aVTZ 13.68/15.66 7.36/8.71 PBE-D3/CBS 12.45/14.32 9.59/11.03 PBE-D3/PW 12.48/14.33 6.99/8.06 PBE-TS/PW 6.65/7.22 13.66/14.51 PBE-TS/tier3 14.47/15.95 10.09/11.42 PBE-TS/tier2 9.94/11.27 13.60/15.11 PBE0-D3/CBS 12.55/14.70 9.09/10.72 PBE0-D3/PW 12.58/14.68 8.40/10.88 PBE0-TS/PW 8.52/10.45 13.63/14.53 PBE0-TS/tier3 13.58/14.56 8.08/10.34 PBE0-TS/tier2 13.58/14.48 8.11/10.32 vdW-DF2/PW 6.55/7.18 13.29/14.28 a The binding energies within 1 kJ/mol error from CCSD(T)/CBS values are highlighted in bold. All b

energies were based on without BSSE correction except for the CCSD(T)/aVTZ value for which BSSE correction was made. bThe CCSD(T)/aVTZ inter-molecular distance was optimized for the BSSE corrected MP2/aVTZ optimized geometry (ref. 38).

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Table 2. Binding energies (kJ/mol) of Cor–CCl4/CBr4.a Stagg Eclip Edge Side M06-2X/CBS 20.0/25.9 19.2/23.7 18.2/20.1 6.5/8.3 M06-2X/aVTZ 25.2/30.3 24.4/28.3 22.4/27.0 8.3/10.2 PBE-D3/CBS 26.9/31.5 26.7/32.8 23.2/28.2 11.1/14.0 PBE-D3/PW 26.8/32.3 26.5/31.9 22.2/26.4 11.0/13.1 PBE-TS/PW 29.9/33.5 29.2/32.6 25.1/27.2 10.8/12.4 PBE-TS/tier3 30.4/34.6 29.9/33.7 25.7/28.4 10.3/11.5 PBE-TS/tier2 29.8/33.5 30.3/32.8 25.5/28.3 10.3/11.5 PBE0-D3/CBS 26.8/33.2 26.4/32.7 23.3/28.2 11.0/11.9 PBE0-D3/PW 27.5/33.5 27.2/32.9 22.9/27.4 10.9/12.9 PBE0-TS/PW 30.3/34.4 30.5/33.5 25.1/28.1 9.9/12.6 PBE0-TS/tier3 30.3/34.1 29.6/33.1 25.8/27.7 10.5/11.9 PBE0-TS/tier2 30.1/33.8 29.5/32.9 25.7/27.5 10.5/11.9 vdW-DF2/PW 31.2/35.2 31.0/34.6 25.6/27.4 10.0/11.2 a The geometries used with non-PW basis sets are based on aVDZ or light-tier2/tier3 basis set.

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Table 3. DFT-SAPT Interaction Energy Components (kJ/mol) at the PBE0AC/aVDZ level on the BSSE corrected MP2/aVDZ geometry of the StagC conformers. Conformer

E es

* Eind

* E disp

* Eexch

δH

Eint

Bz–CCl4 –10.31 –0.71 –24.29 27.18 –1.89 –10.02 22.17 0.84 Bz–CBr4 –9.12 –1.98 –23.32 –11.41 * Ees: electrostatic energy. Eind :effective induction energy including the induction-induced exchange energy; Eind*= Eind + Eind–exch. Edisp*: effective dispersion energy including the dispersion-induced exchange energy; Edisp*= Edisp + Edisp–exch). Eexch*: effective exchange repulsion energy with the induction-induced and dispersion-induced exchange energies excluded; Eexch*= Eexch – (Eind–exch + Edisp– exch)

= Eexch1. (refer to ref. 30). δH: contribution of the third and higher order terms at the uncorrelated

level, which could be included into Eind*. Eint : total interaction energy).

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Table 4. Binding energies (kJ/mol) of Gr–CCl4/CBr4. StagC PBE-D3/PW 34.4/41.9 PBE-TS/PW 41.6/46.2 PBE-TS/tier3 41.5/46.9 PBE-TS/tier2 41.3/46.5 PBE0-D3/PW 34.1/42.2 PBE0-TS/PW 40.3/45.5 PBE0-TS/tier2 39.9/45.5 Vdw-DF2/PW 36.0/38.0

Eclip 32.2/39.9 38.0/43.7 38.5/44.9 38.4/44.5 31.5/39.7 36.6/42.5 37.1/43.3 33.9/36.8

Leg1C 19.7/24.6 21.8/25.3 22.1/25.9 21.7/25.3 18.0/23.4 19.1/23.5 20.2/24.5 18.8/19.5

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Figure Captions

Figure 1. Structures (top and side views) of Bz–CX4 (X = Cl and Br). Figure 2. Stable structures (top and side views) of Cor–CX4. Figure 3. Unit cell geometries of Gr–CX4 used in the periodic calculations. Figure 4. (a) NBO charges of F/Cl/Br in CF4/CCl4/CBr4 (at PBE-D3/aVDZ, PBE0D3/aVDZ(6-31G*), and CCSD/aVDZ levels) and C96H24–CF4/CCl4/CBr4 (StagC structure at PBE/6-31G* level), showing the electron transfer from CF4 to C96H24 and the electron transfers from C96H24 to CCl4/CBr4. (b) The change in NBO charges of CF4, CCl4, and CBr4 molecules with respect to inverse square of the number of C atoms (1/n2) of C24H12, C54H18, and C96H24. Figure 5. Band structures of graphene near the Dirac point (at the PBE-D3/PW level) for (a) the pristine case and (b) CF4, (c) CCl4, and (d) CBr4 adsorbed cases for the StagC geometry.

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Figure 1. Structures (top and side views) of Bz–CX4 (X = Cl and Br).

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Figure 2. Stable structures (top and side views) of Cor–CX4.

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Figure 3. Unit cell geometries of Gr–CX4 used in the periodic calculations.

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Figure 4. (a) NBO charges of F/Cl/Br in CF4/CCl4/CBr4 (at PBE-D3/aVDZ, PBE0D3/aVDZ(6-31G*), and CCSD/aVDZ levels) and C96H24–CF4/CCl4/CBr4 (StagC structure at PBE/6-31G* level), showing the electron transfer from CF4 to C96H24 and the electron transfers from C96H24 to CCl4/CBr4. (b) The change in NBO charges of CF4, CCl4, and CBr4 molecules with respect to inverse square of the number of C atoms (1/n2) of C24H12, C54H18, and C96H24.

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Figure 5. Band structures of graphene near the Dirac point (at the PBE-D3/PW level) for (a) the pristine case and (b) CF4, (c) CCl4, and, (d) CBr4 adsorbed cases for the StagC geometry.

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Adsorption of Carbon Tetrahalides on Coronene and Graphene - The

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