Influence of Boron Substitution on Conductance of Pyridine- and Pentane-Based Molecular Single Electron Transistors: First-Principles Analysis

Abstract

We have investigated the modeling of boron-substituted molecular single-electron transistor (SET), under the influence of a weak coupling regime of Coulomb blockade between source and drain metal electrodes. The SET consists of a single organic molecule (pyridine/pentane/1,2-azaborine/butylborane) placed over the dielectric, with boron (B) as a substituent. The impact of B-substitution on pyridine and pentane molecules in isolated, as well as SET, environments has been analyzed by using density functional theory-based ab initio packages Atomistix toolkit-Virtual NanoLab and Gaussian03. The performance of proposed SETs was analyzed through charging energies, total energy as a function of gate potential and charge stability diagrams. The analysis confirms that the B-substituted pentane (butylborane) and the boron-substituted pyridine (1,2-azaborine) show remarkably improved conductance in SET environment in comparison to simple pyridine and pentane molecules.

Full text

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
1
Influence of Boron Substitution on conductance of Pyridine and
Pentane based Molecular Single Electron Transistors: First
Principles Analysis
Anurag Srivastava1*, B. Santhibhushan1, Vikash Sharma1,2, Kamalpreet Kaur1,2 , Md. Shahzad Khan1, Madura
Marathe3, Abir De Sarkar4 and Mohd. Shahid Khan5
1Advanced Materials Research Group,CNT Lab, ABV-Indian Institute of Information Technology and Management, Gwalior, M.P-474015,
India.
2 VLSI Design Laboratory, ABV-Indian Institute of Information Technology and Management, Gwalior, M.P-474015, India.
3Electronics and Communication Engineering, Maulana Azad National Institute of Technology, Bhopal, M.P. India
4Institute of Nano Science and Technology, Habitat Centre, Phase-10, Sector-64, Mohali, Punjab-160 062
5Department of Physics, JamiaMilliaIslamia, New Delhi 110025, India
ABSTRACT
We have investigated the modeling of boron-substituted molecular single electron transistor (SET), under
the influence of a weak coupling regime of Coulomb blockade between source and drain metal electrodes. The
SET consists of a single organic molecule (pyridine/pentane/1,2-azaborine/butylborane) placed over the
dielectric, with boron (B) as a substituent. The impact of B-substitution on pyridine and pentane molecules in
isolated, as well as SET, environments has been analyzed by using density functional theory-based ab initio
packages Atomistix toolkit-Virtual NanoLab and Gaussian03. The performance of proposed SETs was analyzed
through charging energies, total energy as a function of gate potential and charge stability diagrams. The
analysis confirms that the B-substituted pentane (butylborane) and the boronsubstituted pyridine (1,2-azaborine)
show remarkably improved conductance in SET environment in comparison to simple pyridine and pentane
molecules.
Keywords: Density Functional Theory (DFT), Boron (B), Single-Electron Transistor (SET), 1,2-azaborine
(C4H5NB), butylborane (C4H12B), Charge Stability Diagram, threshold voltage (Vth), Natural Bond Orbital
(NBO).
.
1. INTRODUCTION
In the last few years, the continuous shrinking of the channel length of metal oxide semiconductor field
effect transistors (MOSFET) has confronted limitations from the areas of thermodynamics, quantum mechanics,
and electromagnetics. These limitations forced the scientific community to think of replacing these MOSFETs
with new nanoelectronic devices such as multigate junctionless FETs, single electron transistors (SET), and
carbon nanotube FETs (CNTFET), etc.1 Single-electron devices are highly promising due to their ultra-s mall
size and low power dissipation, and hence their modeling has become an important scientific issue of interest for
researchers. Single electronics deals with the mechanism whereby a single or a very small number of electrons
flow in the device at a time. Hence, the analysis of island/quantum dot plays a very important role in
understanding the quantum tunneling of electrons through the barrier. 2–6 In SET systems, the electrodes are

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
2
strongly coupled with the island, supporting a coherent transport mechanism. This strong coupling enables
hastened tunneling of electrons from source to island to drain, enabling the electrons to retain their original state
information of source.
A schematic of a SET designed by placing two tunnel junctions in series and an island/quantum dot
sandwiched between them is depicted in Fig. 1. In SETs, the current flow is due to controlling the sequential
tunneling of the electrons one by one, in which the gate is capacitively coupled to control the electron tunneling
by shifting the energy levels of the island. The very convincing characteristics of SETs, such as high input
impedance, nano-scale size, and ultra-low power dissipation makes them appropriate for applicat ions in
switching devices, quantum computers, memory design, sensor design, etc.7–13 In the last few years, experiments
and simulations on SETs by the scientific community has made significantly progress. A few recent reports on
density functional theory-based computational investigation of these SET systems for sensors have apperaed.10–
13 Wasshuber14 reported the charging effects of a single electron in tunnel junctions. Further, the mechanism of
electron transport has been observed and illustrated by Fulton and his team.15 In another study,16 it has been
reported that single-electron transport can be observed in two regimes, coherent and non-coherent. The coherent
tunneling has been analyzed through non-equilib rium green’s function method, whereas the non-coherent
tunneling employed in SET has been reported in Refs. 17 and 18. Based on normalization of molecular charges
due to polarization, similar other approaches have been reported elsewhere.18
Fig.1: Schematic of Single Electron Transistor.
2. THEORY AND COMPUTATIONAL DETAILS
The nature of current flow through the tunnel junction is discrete in nature, where the charges aggregate near
the tunnel junction and cross it as a result of sufficient bias (V> Vth, Vth = e/C; where e is the charge of the
electron and C is the selfcapacitance of the island). For transferring one electron to the island, the electrostatic
energy (or Coulomb energy) needing to be supplied to the system is Ec = e2/2C. The controlled tunnel

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
3
phenomenon of SET is possible only if the Coulomb energy is greater than the thermal variations due to the
thermal energy ET = KBT (where KB is the Boltzmann constant and T is temperature). The electrostatic energy
of a system can be calculated in terms of capacitor configurations estimated through capacitance matrix (C) as
given elsewhere,14 and the total charge (q) at any node (a or b) is calculated by the following relationship,
(b= 1, 2 …) --- (01)
Cab = capacitance between the node (a) and node (b).
Vb= potential of other node b.
And the electrostatic energy for charging carriers can be computed as
--- (02)
Where, Q= vector of node charges
V= vector of node voltages
By solving the eq.(02), we can get the total change in energy, required to add one charge (+e) to node b, given
by
--- (03)
(a)
(b)
Fig.2: SET geometry with (a) pentane/ butylborane molecule (b) pyridine/ 1,2-azaborine molecule as island.
Density functional theory (DFT)-based ab initio packages ATK-Virtual Nanolab19 and Gaussian03 have been
used to analyze the boron-substituted molecular SET. Mulliken, NBO charges, and molecular energy spectrum
information have been computed using Gaussian. Pentane-, pyridine-, butylborane- and 1,2-azaborine-based
SETs have been analyzed with gold electrodes20 and a gate dielectric of 3.2 Å thickness with 10 εo dielectric
constant. These organic molecules are placed in the SET environment as shown in Fig. 2. The charging energies
for pristine molecules (pentane and pyridine) as well as boron-substituted molecules (butylborane and 1,2-
azaborine) were calculated in isolated phase as well as for the SET environ ment. The charge stability diagram
and total energy variation as a function of gate potential have been plotted in terms of the obtained charging and
total energies in the SET environ ment. Non-polarized DFT with local density approximation (LDA)21

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
4
exchange–correlation functional and non-equilibrium green’s function (NEGF),22 a widely used method for
predicting electron transport in quantum mechanical systems, have been employed.23–25 The wave functions
were expanded using a doublezeta polarized (DZP) basis set. Boron, a metalloid, positively charged carbo-
cation, which is isostructural and isoelectronic and allows neutral materials to synthesize directly, is used as a
carbon substituent. The total energy calculations were performed concerning the vacuum level by setting energy
zero level to absolute energy throughout the simulation. Neumann boundary conditions with the Poisson solver
method has been employed to assume the zero component of normal electric field at the boundaries.
Fig.3: Electron density Isosurface plots (a & c) at an Isovalue = 1.816 and Cutplane plots (b & d) for Pyridine (a & b) and
1,2-azaborine (c & d).
3. RESULTS AND DISCUSSION
3.1. B-substitution in Pyridine
Pyridine (C5H5N), tainted with boron by replacing the carbon atom just adjacent to nitrogen forms 1,2-azaborine
(C4H5NB). The electron charge density, Mulliken population, molecular energy spectrum data, total energy,
bond lengths and bond angles have been computed for pure as well as a new molecule. The electron charge
density analysis for pyridine and 1,2-azaborine has been depicted in Fig. 3, where both the isosurface plots (at
an isovalue of 1.816) and cutplane plots are shown for better understanding of boron impact on electron charge
density. For pure pyridine, the electron charge density is almost equally distributed throughout the ring except at
the position of nitrogen, which holds the peak with highest charge density computed as 4.25 e/ Å3. Since, in
pyridine, the lone pair belongs to one of the p-orbital of sp2 hybridization and is heavily localized, hence does

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
5
not participate in delocalization or conjugation. The new molecule formed due to boron substitution, 1,2-
azaborine, illustrates a very interesting result with electron density deserted at the position of boron, even as the
nitrogen holds the peak with a charge density of 3.82 e/Å3. The reason is that nitrogen holds a lone pair of
electrons and donates them to boron which is electron-deficient, forming a coordinate covalent bond. However,
the cause of the charge density desertion in boron might be due to the back donation of electrons by boron to the
nitrogen atom through π* back donation. As a consequence, the system is said to have a delocalized electron
that may bear high mobility.
Fig.4: (a) 1,2-azaborine and (b) butylborane, with atoms provided numbering for usage during the analysis. (B11 can be
replaced by C11 for Pyridine, and B17 by C17 for Pentane)
Further, to analyze the charge distribution, partial charges on pure pyridine (in parentheses) and 1,2-
azaborine have been computed and tabulated in Table I, and also seen in Fig. 4. The charge analysis (NBO and
Mulliken) has been carried out using Gaussian03 software26 on the same optimized geometry obtained from
ATK-VNL. The basis set used for the present calculations are Gaussian type orbitals with polarized and diffuse
extensions, namely 6-311++G(d,p). The charge transfer analysis has been performed through two theoretical
approaches, natural bond orbital (NBO) and Mulliken. From the molecular point of view, NBO yields
comparatively more precise results than the Mulliken, as the former is based on a localized orbital concept. The
charge distribution obtained through both approaches is the same in nature as seen from Table I, but
quantitatively different. For further scrutinizing of the results, the NBO values have been considered. NBO
analysis confirms that the boron has lost a charge of 0.611e to its neighboring atoms in 1,2-azaborine. As a
result, nitrogen gained a charge of 0.675e after boron substitution, i.e., it is 0.223e higher in quantity than it
possessed formerly. C4 carbon has also gained an excess charge of 0.118e in comparison to the value it
possesses in a pure state. Interestingly, hydrogen (H10) which lost a charge of 0.186e to carbon in pure pyridine
has gained a charge of 0.09e after the boron substitution. This confirms the transfer of charge from boron to its
neighboring atoms in the new molecule 1,2- azaborine. Analysis of the molecular energy spectrum has been
performed using Gaussian03 to observe the change in the highest occupied molecular orbital– lowest
unoccupied molecular orbital (HOMO– LUMO) gap as an effect of boron substitution. The pyridine molecule in
its pure state was found to have a HOMO–LUMO gap of 6.09 eV, decreasing to 5.92 eV after substitution,
indicating the improved conductivity. The formation energy for 1,2-azaborine has been computed as 4.027 eV,
by using the following equation,

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
6

   
     
--- (04)
Remarkably, the C1–N5 bond length of 1,2-azaborine decreases to 1.303 Å from 1.3529 Å which is that of
pyridine. This reduction might be due to the reduced repulsion between the lone pair of nitrogen and the C1–N5
bonded electrons, as the lone pair gets dispersed over N5–B11 in 1,2-azaborine. Supporting this statement, the
bond length of N5–B11 (1.372 Å) is perceived to be higher in comparison to the N5–C11 bond length (1.352 Å)
of pyridine. Further, the C1–N5–C11 (C1–N5–B11) bond angle was measured as 119.570 (133.380).
3.2. B-substitution in Pentane
In another case, the pentane (C5H12) molecule, tainted with boron by replacing an end carbon atom, forms
butylborane (C4H12B) which was optimized. A similar analysis as described in the previous section for pyridine
has also been performed for pentane. The electron charge density plot for pentane (with and without boron
substitution) is shown in Fig. 5, where both the isosurface plots at an isovalue of 1.376 and cutplane plots are
presented. Although it is not possible to view the complete structure of the pentane molecule in the cutplane plot
due to its irregular structure, the view presented in the plots well describes the electron charge density
distribution for the molecule. In pure pentane, the electron charge density is distributed in such a way that the
carbon atoms hold a relatively higher charge density than hydrogen, and the highest charge density measured on
carbon atoms is 2.03 e/Å3, whereas in butylborane, the maximum charge density is observed as 2.06 e/Å3 and a
desolation of charge density was observed in place o f boron. These statements are best verified through NBO
analysis presented in Table II, for the corresponding numbering of atoms and also in Fig. 4.

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
7
Fig.5: Electron density Isosurface plots (a & c) with Isovalue = 1.376 and Cutplane plots (b & d) respectively for Pentane (a
& b) and butylborane (c & d).
The NBO analysis of pure pentane shows a charge gain by all the carbons, while all the hydrogens lost
charges. When the carbon is replaced by boron, a relative charge loss of 0.589e is observed in boron (B17) in
comparison to carbon (C17). In contrast, the hydrogens surrounding boron (H14, H15, H16), which lost a charge
of approximately 0.19e in pure cases, have gained a relative charge of approximately 0.264e due to boron
substitution. Pentane in its pure form assumed a HOMO– LUMO gap of 8.51 eV, while a gap of 6.83 eV is
observed for butylborane. The diminished HOMO–LUMO gap after substitution is certainly an indication of the
mo lecule’s enhanced conductivity. Further, to analyze the structural properties of the molecule, the formation
energy of butylborane has been calculated as 6.274 eV along with variations in the bond angles and bond
lengths scrutinized with boron substitution. The bond lengths of B17 (C17)–C11, B17 (C17)–H14, B17 (C17)–
H15 and B17 (C17)–H16 are perceived to be 1.681 Å (1.511 Å ), 1.214 Å (1.098 Å ), 1.275 A ° (1.097 Å ) and
1.213 Å (1.098 Å ), respectively. The bond angles of boron with the surrounding hydrogen and carbon atoms
were measured and compared with that of pentane. The calculated bond angles for H14–B17(C17)–H15, H15–
B17(C17)–H16 and, H14–B17(C17)–H16 are 110.990 (107.390), 112.120 (107.390) and 119.150 (107.220),
respectively. Here, it can be seen that the bond angles and bond lengths at the boron site increase due to boron
substitution.
3.3. Butylborane and 1,2-azaborine as SET Islands
The conductance and stability analysis of pristine and boron-substituted molecules of pyridine and
pentane have been investigated by placing them in a SET environment. Here, all four molecules have been
considered as islands by placing them over the gate dielectric in the SET. The charging energy of 1,2-azaborine
has been computed by calculating the total energies at different charge states of the molecule, i.e. -2, -1, 0, 1,
and 2, in both the isolated as well as the SET environments for pentane, butylborane, pyridine and 1,2-
azaborine, listed in Table III. In the SET environment, the total energy and changes in the total energy of islands
due to the applied electric field play an important role. As far as the charging energy is concerned, the smaller its
value, the easier it is for the system to overcome the coulomb blockade. The charging energies were calculated
using the following relationship,
EI = E (N) – E (N-1) --- (05)
where N is the number of electrons of the island.
For the pentane molecule in the gas phase state, EI is calculated as 10.1366 eV, close to the experimental
value 10.28 eV.27 Similarly, the EI calculated for the pyridine molecule is 9.18830 eV, also in good agreement
with its experimental counterpart of 9.26 eV.27

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
8
(a) Pentane based SET
(b) Butylborane based SET

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
9
(c) Pyridine based SET
(d) 1,2-azaborine based SET
Fig. 6: Total energy as a function of gate voltage plotted for (a) pentane [C5H12] (b)Butylborane [C4H12B] (c) Pyridine
[C5H5N] and (d) 1,2-azaborine [C4H5NB] based SET. Different charged states of the molecule are shown by different
colored curves blue (-2), green (-1), red (0), turquoise (1), and violet (2).
The total energy has been computed as a function of gate voltage (VG) varying from -8 V to 8 V, for different
charge states (-2, -1, 0, 1, 2) of the molecules in the SET environment, plotted in Fig. 6a–d. The total energy has
been calculated using the following equation,
=+ () 2 --- (06)

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
10
Where, α is the gate coupling constant, q is charge on the molecule, VG the gate voltage, e is charge of an
electron and β a constant. In the above relationship, there are two components: first, the linear component which
is dependent on q, and second, the quadratic component due to the polarization of the molecular island,
independent of q, and hence neglected. The equation henceforth is directly proportional to αqV
G and the
computed values of a for different island molecules are given below,
α (C5H12 ) = 0.6451
α (C5H5N) = 0.7527
α (C4H12B) = 0.6240
α (C4H5NB) = 0.7515
From Fig. 6a–d, a linear relationship between total energy and gate voltage for different charge states
has been observed. However, they are not completely straight lines as they look rather curved, but the relative
plotting of the five charge states in a single window makes them look linear. If the total energy of a particular
charge state is lowest at a particular gate voltage, it implies that the molecule is most stable at that charge state
corresponding to that voltage. In the SET environment at zero gate voltage as shown in Fig. 6a and c, the
pentane (C5H12) and pyridine (C5H5N) have less total energy in their neutral state and hence are considered to be
more stable in their neutral state at zero gate voltage. However, in the case of butylborane (C4H12B), although
the neutral state is found to be the most stable state at zero gate voltage, a sharp transition to a negatively
charged state is noted with respect to the gate voltage. In the case of 1,2-azaborine (C4H5NB), a negatively
charged state has been observed to be the most stable at zero gate voltage. The transition among the charge
states with respect to the gate voltage variation is shown in Fig. 6a–d. Of these studied molecules, the 1,2-
azaborine molecule show a very good transition among the charge states subjected to gate voltage variation. In
general, as the positive gate bias increases, the negative charge states (i.e., -1, -2) show a considerable decrease
in total energy, makes them more stable at positive gate voltages. However, at negative gate voltages, positive
charge states (i.e., +1, +2) are more stable as compared to other charge states, due to the shift in HOMO and
LUMO levels with gate voltage. On application of a positive gate voltage, the LUMO level shifts below the
electrode Fermi level and subsequently attracts an electron, which is responsible for making the molecular island
negatively charged, whereas, at negative gate voltage, the HOMO level shifts above the electrode Fermi level
resulting in the fleeing of an electron from the island and charging it to positive.
(a) Pentane based SET (b) Pyridine based SET

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
11
(c)Butylboranebased SET
(d) 1,2-azaborine based SET
Fig.7: Charge stability diagrams for (a) Pentane (b) Pyridine (c) butylborane and (d) 1,2-azaborine based SETs. The number
of charge states in the bias window for given bias potentials are given by the specific color. The color map is: blue (0), light
blue (1), green (2), Yellow (3), red (4).
For a better analysis of the conductance of SETs, the charge stability diagrams have been plotted for different
gate bias voltages, where the conductance is directly proportional to the number of energy levels existing in the
bias window.16 We have earlier tested different acene series of molecules as SET islands as part of our study to
identify the best acene molecular SET, reported elsewhere.28–30 It is a well-known fact that the charge transfer in
a SET occurs when it overcomes the Coulomb blockade region, so to overcome the Coulomb blockade, a
sufficient charging energy may be supplied through the adjustment of the gate and source–drain potentials. For
the given values of the gate and source–drain bias, the number of molecular energy levels inside the bias
window is given by the color codes in Fig. 7a–d. Concerning the charge stability diagrams of pentane- and
pyridinebased SETs, shown in Fig. 7a and b, at zero gate and source–drain bias, no conduction is possible, as
the SET operating point lies in the dark blue region where no energy level is available on the island to support
the conduction. The conduction would not be possible even if the gate voltage varies from -15 V to 15 V
keeping the source–drain bias zero. For the cases of pure pentane and pyridine-based SETs, high excitation
energies are needed to bring the energy levels into the bias window, so as to make the device conduct.
Excitation energy is the energy supplied by adjusting the bias potentials so as to bring the device operating point
from the dark blue region (no conduction) to the light blue region (one energy level available for conduction).
Figure 7 shows that 1,2-azaborine and butylborane molecular SETs need relatively less excitation energy in
comparison to their pristine counterparts. Butylborane conducts more efficiently when the gate is negatively
biased in comparison to the case when it is positively biased, the reason being that the number of energy levels
increases promptly in the earlier case, whereas for 1,2-azaborine, at positive gate voltages, the required
excitation energy is very low and in turn relatively higher conduction, as the energy levels surges rapidly in
comparison to the case when the gate is negatively biased, subjected to the variation of source–drain bias. A
slight variation in bias potentials switches the 1,2-azaborine SET from OFF state to ON state in comparison to
other SETs studied in this work.Of the SET models discussed in the present work, the 1,2-azaborine SET
possesses higher conductivity as a result of improved electron mobility due to delocalization of the nitrogen
electron lone pair in the 1,2-azaborine molecule.

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
12
4. CONCLUSION
The present work discusses DFT-based ab initio analysis of the influence of boron substitution in place of
selected carbon atoms of pentane/pyridine molecules in isolated as well as in SET environments. The
substitution effect has been analyzed in terms of electron density, Mulliken population, NBO, molecular energy
spectrum data, structural analysis, charging energies and charge stability diagrams. A substitution of single atom
of carbon by boron has resulted in the formation of a few interesting molecules, with remarkable deviation in
characteristics from their host molecule. The study supports that the 1,2-azaborine molecule shows significantly
high conductance inthe SET environment in comparison to its contenders and, hence, it is confirmed that boron
substitution to the island molecules plays an important role in the overall conductance and hence performance of
the SET.
Acknowledgement
The authors are extremely grateful to ABV-Indian Institute of Information Technology and Management,
Gwalior (ABV-IIITM) for providing the infrastructural support to the present research work. Authors are
thankful to Dr. Md. Mushtaque, Assistant professor at Al-Falah University, Faridabad, Haryana and Dr.
SadhanaShrivastava, Professor of Chemistry from SLP College, Jiwaji University, Gwalior for their valuable
scientific discussions.
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Table.1.1:Mulliken as well as NBO charges for 1,2-azaborine and Pyridine [In closed brackets].
1,2-azaborine [Pyridine]
Mulliken (in e)
NBO (in e)
C-1
-0.198 [-0.370]
0.170 [0.053]
C-2
0.046 [0.101]
-0.118 [-0.245]
C-3
-0.051 [-0.220]
-0.239 [-0.167]
C-4
-0.338 [0.100]
-0.363 [-0.245]
N-5
-0.251 [-0.073]
-0.675 [-0.452]
B-11 [C-11]
0.176 [-0.371]
0.611 [0.053]
H-6
0.170 [0.162]
0.204 [0.186]
H-7
0.161 [0.162]
0.167 [0.211]
H-8
0.183 [0.162]
0.20 [0.208]
H-9
0.155 [0.162]
0.20 [0.211]
H-10
-0.044 [0.162]
-0.09 [0.186]

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
14
Table.1.2:Mulliken as well as NBO charges for butylborane and Pentane [In closed brackets].
Butylborane [Pentane]
Mulliken (in e)
NBO (in e)
C-1
-0.555 [-0.589]
-0.571 [-0.569]
C-5
-0.167 [-0.113]
-0.361 [-0.378]
C-8
-0.012 [-0.116]
-0.457 [-0.376]
C-11
-0.420 [-0.113]
-0.206 [-0.378]
B-17 [C-17]
0.010 [-0.589]
0.020 [-0.569]
H-2
0.144 [0.137]
0.204 [0.198]
H-3
0.142 [0.134]
0.197 [0.192]
H-4
0.142 [0.134]
0.197 [0.192]
H-6
0.139 [0.123]
0.190 [0.185]
H-7
0.139 [0.123]
0.190 [0.185]
H-9
-0.131 [0.110]
0.211 [0.184]
H-10
0.131 [0.110]
0.211 [0.184]
H-12
0.173 [0.123]
0.195 [0.185]
H-13
0.173 [0.123]
0.195 [0.185]
H-14
-0.06 [0.137]
-0.072 [0.198]
H-15
-0.06 [0.134]
-0.072 [0.192]
H-16
-0.053 [0.134]
-0.072 [0.192]

Srivastava, Anurag, et al. "Influence of Boron Substitution on Conductance of Pyridine-and Pentane-Based Molecular Single
Electron Transistors: First-Principles Analysis." Journal of Electronic Materials 45.4 (2016): 2233-2241.
15
Table.2:Charging energies for pentane (C5H12), pyridine (C5H5N), butylborane (C4H12B) and 1,2-azaborine
(C4H5NB) molecules in isolated and SET environments.
Charge State
Charging Energy (eV) in
Gas Phase
Charging Energy (eV) in
SET environment
Pentane
+2
-15.8784
-10.827360
+1
-10.1366
-9.052486
0
4.6699
2.216419
-1
9.1418
2.866667
Butylborane
+2
-15.691939
-10.750355
+1
-9.904384
-9.078688
0
-3.415705
-6.892774
-1
8.539880
2.840790
Pyridine
+2
-16.18040
-8.80295
+1
-9.18830
-8.08955
0
1.89510
-1.78621
-1
8.22320
-0.38084
1,2-azaborine
+2
-15.71655
-8.40824
+1
-9.01428
-8.49604
0
-2.25330
-6.37902
-1
7.92966
-0.59570