Journal of Nano Chemical Agriculture , Vol(1) , No(3) 94

The investigation of NMR parameter of drug binding to Single Wall Carbon Nanotube

Z.Yousefian1, 2*, N. Shadmani3

1* Department of Chemistry, Shahre-Rey Branch, Islamic Azad University, Tehran, Iran

2Young Researchers and Elite Club, Shahre-Rey Branch, Islamic Azad University, Tehran, Iran 3Young Researchers and Elite Club, Rasht Branch, Islamic Azad University, Rasht, Iran

*Corresponding author’s E-mail:zohreh_yousefian@yahoo.com

Abstract

At the present study, Clonidine drug were added to zigzag single walled carbon nanotubes (CNT) with (5,

0) structure and a length of 50A. Then NMR different parameters of Drug-CNT complex such as magnetic

shielding tensor (σ ,ppm), shielding asymmetry (η), magnetic shielding constants (σ iso), anisotropic magnetic

shielding tensors (σaniso), Chemical shifts (δ) was studied in theory level of HF/6-31G* in gas phase. The

results obtained from a comparison between tables and charts came up for discussion and analysis.

Keyword

Single walled carbon nanotube (CNT) , Clonidine, Drug , NMR

Introduction

Carbon nanotubes were discovered almost 15

years ago. The first report by Iijima [1] was on the

multi wall form, coaxial carbon cylinders with a

few tens of nanometers in outer diameter. Two

years later single walled nanotubes were

reported [2, 3]. They are typically between 1 and

1.5 nm in diameter, but several microns in length.

After a slow start in the mid 90’s the field

suddenly exploded two years ago. A first

application – displays made out of field emitting

multiwall tubes – is planned to be commercially

available during the next years. Other proposed

applications include, e.g., nanotubes in

integrated circuits, nanotubes actuators, or

nanotubes for hydrogen storage [4-8]. From a

physics point of view they are probably the

best realized example of a one-dimensional

system.

Nano technology is an advancing method with

many ways for unlocking problems, especial in

medical science. By performing more research on

this technology, treat can be found for diseases

that have no cures until now. Therefore,

nanotechnology can effect on life like are

volution. One of the exciting classes of nano

materials is carbon nanotubes (CNTs), which

possess characteristics suitable for many

applications as delivery vehicles of biologically

important molecules in view of possible

biomedical applications, such as vaccination and

gene or drug delivery. Scientists from different

fields of science are just beginning to solve my

steries and hypo the size about CNT-gen

complexes. A useful devise to achievement these

purposes is theoretical methods. [9, 10]

Ideally, the nanotubes will locate to a specific

site in the body, through its functionalized

surface, and release its contents. The major

advantage with this form of targeted drug

delivery is the possibility of reducing the many

adverse side effects experienced by patients [11-

16] hence throughout various field of science and

technology, a push towards the use of Nano-

95 The investigation of NMR parameter

scale technology such as Single wall carbon

nanotubes is on the move. One area where CNTs

work is already well under way is within the field

of drug delivery. CNTs make possible bonding to

drugs [17].

The primary goal of this study was to examine the

binding of Clonidine drug with zigzag single

walled carbon nanotubes (CNTs) with (5, 0)

structure and a length of 50A.

The secondary goal of this study was to

investigate NMR parameter of Drug-SWCNT

complex. [18]

Methodology

In our model, Clonidine drug was attached

covalently to carbon nanotube (CNTs) with (5, 0)

structure and a length of 50A.

All calculations were performed using Gaussian

09 software package. Geometrical optimizations

of Drug, single point calculation and NMR

parameters were carried out in gas phase with

the Hartee -Fock and B3LYP methods coupled to

6-31g* and 6-31g basis sets for all atoms.

The most common type of ab initio calculation is

called a Hartee- Fock calculation (abbreviated

HF), in which the primary approximation is called

the central field approximation. A method, which

avoids making the HF mistakes in the first place,

is called Quantum Monte Carlo (QMC). There are

several flavors of QMC variational, diffusion and

Green's functions. These methods work with an

explicitly correlated wave function and evaluate

integrals numerically using a Monte Carlo

integration [19, 20]. In general, ab initio

calculations give very good qualitative results and

can give increasingly accurate quantitative results

as the molecules in question become smaller

[21].There are three steps in carrying out any

quantum mechanical calculation in Hyper Chem.

7.0 program package [22]. First, prepare a

molecule with an appropriate starting geometry.

Second, choose a calculation method and its

associated options. Third, choose the type of

calculation with the relevant options. For

example we calculated H, C, N, Cl NMR spectral

parameters for the interaction of Clonidine drug

with CNT in gas phase by the HF/6-31g*method.

The chemical shielding tensor describes how

the shielding varies with the molecular

orientation. The three principal components of

this tensor are often given by:

σ11 ≤ σ22 ≤ σ33

The values of the shielding tensor are frequently

expressed as the isotropic and anisotropic parts

(σiso and σaniso) and the shielding asymmetry (η) .

[23, 24]

Results and Discussion

Molecular Geometry

Fig. 1, Shows the graphical representations of

the optimized geometry of drug–CNT. In the

figure, the Cl atoms are shown by green colors,

white spheres are H atoms, blue sphere is N and

gray sphere is C. Selected geometrical

parameters for Clonidine drug CNT are also

shown in Fig.1.

Journal of Nano Chemical Agriculture , Vol(1) , No(3) 96

Fig.1.Optimized geometries of Clonidine and Clonidine drug-CNT obtained at HF/6-31G level

Nuclear Magnetic Resonance Parameters

NMR is based on the quantum mechanical

property of nuclei. The chemical shielding refers

to the phenomenon, which is associated with the

secondary magnetic field created by the induced

motions of the electrons that surrounding the

nuclei when in the presence of an applied

magnetic field [25]. In general, the electron

distribution around a nucleus in a molecule is

more spherically symmetric. Therefore, the size

of the electron current around the field, and

hence the size of the shielding, will depend on

the orientation of the molecule within the

applied field B0.

In the present paper, total dipole moments of

drug interaction with CNT in gas phase have been

explored and NMR computations were done by

Gaussian 09 suite of programs. The calculated

magnetic shielding tensor (σ ,ppm), shielding

asymmetry (η) and the chemical shift tensor (δ)

calculated for C, H, N and Cl nuclei in the active

site of Clonidine drug and for carbon atoms of

the open end of a CNT system in gas phase are

presented in Table 1. Also, the graphs of

calculated isotropic magnetic shielding constants

σiso (ppm), anisotropic magnetic shielding tensors

σaniso (ppm), Chemical shifts δ (ppm) and shielding

asymmetry (η) versus the number of atomic

centers for selected atoms of drug -CNT system

are displayed in Figs. 2a-c respectively.

As was expected, the NMR shielding tensors of H,

C, N, and Cl nuclei are drastically affected by the

atom to which they are bonded and by the type

of the bond to the neighboring atom. The results

obtained give strong evidence that

intermolecular interactions play a very important

role in determining the H, C, N and Cl NMR

chemical shielding tensors. Some systematic

trends appeared from the analysis of the

calculated values.

According to Figure2a, it is obvious that one atom

in drug-CNT system has maximum value in

compare to the other atoms of this structure and

this value belongs to 33Cl. Anisotropic chemical

shielding is one of the other parameters that

were checked in this work. From Figure 2b it has

been found that the maximum value of σaniso in

drug-CNT system is related to 16C.

The results of investigating chemical shift tensor

indicate that 32Cl have been shown to be the

largest value of (δ) in system as drug interacted

with CNT and our knowledge about drug

interacted to CNT has been specified that C

number 31 show the largest intermolecular

effects in (η) component (Fig. 2d).

97 The investigation of NMR parameter

Conclusion

NMR chemical shielding tensors in the

methods framework makes it possible to study

the chemical shift of carbon nanotubes. The

calculated parameters reveal that Cl57 and H83

atoms have the largest and smallest anisotropic

magnetic shielding (σaniso) constants among the

other nuclei, respectively.

The Cl57 has the largest but N62 has the

smallest chemical shift (δ) constants among the

other atoms, respectively. The diagrams consist

of σiso, σaniso and η show all shielding values but

∆σ, δ show more negative shielding values at the

HF in 6-31G* basis set.

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Table1. Components of the magnetic shielding tensor (σ, ppm), shielding asymmetry (η) and the chemical

shift tensor (δ) calculated for C, H, N and Cl nuclei in the active site of Clonidine drug and for carbon atoms

of the open end of a CNT in gas phases at HF level with the 6-31G* basis set

σ11 σ11

Atoms σ22 η Atoms σ22 η

33 δ 33 δ

-637.903 -205.081

16C -146.819 2.1718 0.39 37N 18.9341 60.7706 0.62

833.1764 195.2738 -491.084 406.1945 201.1131 -224.016

-27.4424 -81.4283

26C 62.3164 76.5701 0.68 38C 37.2258 83.3807 0.61

165.2638 137.8214 89.7588 191.1532 109.7249 -118.654

-21.4359 -129.917

27C 74.3248 60.7113 0.75 39N 92.7911 191.107 0.11

205.135 183.6991 109.3743 347.1001 217.1832 -222.708

-31.3291 20.6434

30C 59.2903 70.0129 0.76 48H 25.4223 25.8038 0.84

170.5161 139.187 -90.6194 9.1762 29.8196 -4.7789

-15.762 19.6648

31C 72.2245 74.2898 0.95 51H 28.6523 29.4006 0.83

173.9076 158.1456 -87.9865 17.2266 36.8914 -8.9875

663.5445 14.176

32Cl 816.6251 719.4868 0.22 52H 23.5228 21.6918 0.67

403.2994 1066.844 250.2188 20.5244 34.7004 11.1776

687.0149 22.7438

33Cl 829.9645 740.9236 0.23 53H 26.5296 26.1305 0.59

374.9403 1061.955 231.9907 7.9708 30.7146 5.6926

151.9829 22.9016

34N 201.0279 206.7937 0.76 54H 27.3878 26.1813 0.57

92.3243 244.3072 -49.045 10.1788 33.0804 5.696

82.2142 14.1398

35C 145.1186 158.8151 0.56 55H 31.1369 32.9595 0.78

112.1122 194.3264 -62.9044 32.1716 46.3114 -16.9971

97.5868 -6.546

36C 138.4438 132.6744 0.75 56H 17.6022 9.8818 0.51

87.4834 185.0702 46.6264 56.0167 49.4707 31.8685

99 The investigation of NMR parameter

(a)

(b)

(c)

(d)

Figure2. The graphs of a) , b) σaniso , c) δ , d) η of propose atoms of drug binding to CNT in gas phases

at the HF/6-31G* basis sets.

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