Key factors in determining the arrangement of π-conjugated oligomers inside carbon nanotubes

Yumura, Takashi; Yamashita, Hiroyuki

doi:10.1039/c5cp03433g

Cited by 14 publications

(26 citation statements)

References 54 publications

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“…Previously, we employed dispersion-corrected DFT calculations (B97D function) , in Gaussian 09 to examine the thermodynamically stable arrangements of DANS molecules inside a carbon nanotube . The B97D functional, where empirical dispersion correction is included to the GGA B97 function, have be used for the study of van der Waals complexes and molecules inside nanotubes. − According to ref , B97D calculations can yield potential energy surfaces in benzene dimers and between methane and benzene, being consistent with those obtained from coupled cluster using perturbative triple excitations (CCSD(T)) that is accurate to evaluate dispersion interactions. In fact, their B97D-obtained interaction energies for equilibrium distances are in agreement within a few tenths of a kilocalorie per mole with the CCSD(T) results .…”

Section: Calculation Methodsmentioning

confidence: 62%

Kinetic Control in the Alignment of Polar π-Conjugated Molecules inside Carbon Nanotubes

Yumura

Yamamoto

2018

J. Phys. Chem. C

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Dispersion-corrected density functional theory (DFT) calculations analyze potential energy surfaces (PESs) for the insertion of a certain polarized π-conjugated molecule, p-(dimethylamino)-p′-nitrostilbene (DANS), inside an (m,m) carbon nanotube (n×DANS@(m,m)), where n is the number of inner guests. The current study considered two types of DANS alignments as the dimer structures: linear and stacked alignments, where their dipole moments are oriented in parallel. DFT calculations revealed that a single DANS insertion into a tube with a diameter of approximately 1.0 nm spontaneously proceeds through attractive host–guest interactions. From an end to the middle of a tube, various metastable states and a global minimum structure appear. In 2×DANS@(m,m), which is assumed to be generated by the insertion of another molecule into the tube that already contains one guest, significant roles of intermolecular interactions are found to distinguish their PESs from the 1×DANS@(m,m) case. In addition, the strength of the intermolecular interactions varies depending on the inner DANS dimer alignment and host tube diameters, and thus, striking contrasts were found in PESs for 2×DANS@(m,m). In the formation of linearly aligned DANS molecules inside a tube, the PES is almost identical to that in 1×DANS@(m,m) due to very weak intermolecular interactions. By contrast, intermolecular interactions between the parallel stacked DANS molecules are sufficiently stronger to distinguish their PESs from those in 1×DANS@(m,m); attractive (repulsive) intermolecular interactions within the (8,8) ((7,7)) tube stabilize (destabilize) PESs that are involved in their metastable states and global minimum structure. More importantly, in the stacked alignments, we found the activation energy for the transformation from a metastable state to a global minimum, for which the value decreases in the following order: 20 kcal/mol for 2×DANS@(7,7) > 13 kcal/mol for 2×DANS@(8,8). According to the DFT findings, one can kinetically control the alignments of the DANS molecules inside a thicker tube (i.e., (8,8) tube). In fact, through temperature optimization in heat treatments where the above-mentioned activation energy cannot be overcome, a one-dimensional array of DANS molecules can be formed inside a thicker tube despite its thermodynamic instability. Since linear DANS alignments are responsible for maximizing static hyperpolarizability, the kinetic control technique can expand the diameter ranges of tubes as hosts for DANS guest aggregates exhibiting a significant second-order nonlinear optical response.

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Section: Calculation Methodsmentioning

confidence: 62%

Kinetic Control in the Alignment of Polar π-Conjugated Molecules inside Carbon Nanotubes

Yumura

Yamamoto

2018

J. Phys. Chem. C

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“…In fact, B97D calculations estimated interaction energies for a weakly bound pair of molecules that were in agreement within a few tenths of 1 kcal/mol with CCSD(T) results . Since cost-effective B97D calculations have exhibited good performance in reproducing the interaction energies obtained from accurate CCSD(T) calculations, our previous studies employed B97D calculations to successfully reveal key interactions determining the structures of π-conjugated guest molecules inside tubes. − On the other hand, other researchers have used the M062X functional to investigate how C 60 interacts with CPP as well as how two CPPs interact with each other. − …”

Section: Methods Of Calculationmentioning

confidence: 76%

Energetics of Hybrid Structures between Cycloparaphenylene and Carbon Nanotubes: A Dispersion-Corrected Density Functional Theory Study

et al. 2020

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Dispersion-corrected density functional theory (DFT) calculations examined energetically preferable hybrid structures between [13]cycloparaphenylene ([13]CPP) and an armchair (m,m) tube (5 ≤ m ≤ 9). Tube-in-ring and ring-on-tube structures, denoted by (m,m)@[13]CPP and [13]CPP–(m,m), respectively, were considered. DFT-based energy-decomposition analyses revealed that the key factors determining the stability of the hybrid structures are attractive long-range interactions between [13]CPP and the (m,m) tube and the energy penalty required for the deformation of [13]CPP. The long-range interactions in (m,m)@[13]CPP become more significant with an increase in the tube diameter. The [13]CPP deformation in (m,m)@[13]CPP varies with the degree of deviation between the radius difference between [13]CPP and a tube (Δr) and the van der Waal contact distance between two carbon atoms (3.35 Å). Accordingly, the stability of (m,m)@[13]CPP depends on the tube diameter. Particularly, (8,8)@[13]CPP, whose Δr is close to 3.35 Å, is highly stabilized among (m,m)@[13]CPP because of a negligible energy penalty for the [13]CPP deformation. In contrast, the stability of [13]CPP–(m,m) is less sensitive to the tube-diameter, and their attractive long-range interactions are weaker than those in (m,m)@[13]CPP. Consequently, a tube-in-ring structure whose radius difference is close to 3.35 Å is the most preferable among hybrid structures between [13]CPP and an (m,m) tube.

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“…Carbon nanotubes , have nanometer-sized inner volumes that can contain various π-conjugated molecules. − Filling the interior of a nanotube with π-conjugated molecules has attracted attention because their molecules are arranged in a unique fashion that cannot be found in their crystal structures . Under nanotube surroundings, inner π-conjugated molecules are oriented by attractive host–guest interactions, and at the same time, their molecules are arranged by attractive guest–guest interactions. − Therefore, the unique molecular arrangement inside a nanotube is due to nanometer-size confinement. In general, molecular arrangement is essential for determining their electronic properties, and accordingly, π-conjugated molecules inside carbon nanotubes exhibit characteristic electronic properties compared with those in their crystals. − …”

Section: Introductionmentioning

confidence: 99%

Roles of Carbon Nanotube Confinement in Enhancing Second-Order Nonlinear Optical Properties of Triiodobenzene Aggregates

2021

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Dispersion-corrected density functional theory (DFT) calculations were employed to investigate stable structures of triiodobenzenes (BzI3) inside an armchair (m,m) carbon nanotube (m = 7–9), denoted by n × BzI3@(m,m), where n is the number of guests (n = 1–4). Three BzI3 isomers were considered: 1,3,5-, 1,2,4-, and 1,2,3-BzI3. DFT calculations found that nanotube confinement has an impact on n × BzI3@(m,m) structures, featuring guest orientation, positioning, and alignment. Then, we estimated a threshold value of the diameter of a tube containing BzI3 monomer in a certain orientation without repulsive host–guest interactions (D threshold). To represent the degree of nanotube confinement in 1 × BzI3@(m,m), we obtained ΔD small values by subtracting the smallest limit of D threshold of the guest from the host–tube diameter (D). Negative ΔD small values indicate strong confinement, and positive values less (much larger) than 1.0 Å indicate medium (weak) confinement. The strong and medium confinement in n × BzI3@(m,m) form a linear alignment of guests in parallel orientation with the smallest D threshold value. Reflecting from the different degrees of nanotube confinement, various types of intermolecular interactions operate. DFT calculations found that I–I intermolecular interactions are key in enhancing the second-order nonlinear optical properties of n × BzI3@(m,m). As a result, n × 1,2,4-BzI3@(8,8) with medium nanotube confinement has the most significant hyperpolarizability.

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Key factors in determining the arrangement of π-conjugated oligomers inside carbon nanotubes

Cited by 14 publications

References 54 publications

Kinetic Control in the Alignment of Polar π-Conjugated Molecules inside Carbon Nanotubes

Kinetic Control in the Alignment of Polar π-Conjugated Molecules inside Carbon Nanotubes

Energetics of Hybrid Structures between Cycloparaphenylene and Carbon Nanotubes: A Dispersion-Corrected Density Functional Theory Study

Roles of Carbon Nanotube Confinement in Enhancing Second-Order Nonlinear Optical Properties of Triiodobenzene Aggregates

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