Synthesis, structure, third-order nonlinear optical properties and Hirshfeld surface analysis of tetrakis(azepanium) hexachlorostannate(IV) dichloride and tetrakis(azepanium) hexabromostannate(IV) dibromide

Article abstract of DOI:10.1016/j.molstruc.2020.129515

The new organic-inorganic hybrids of tetrakis(azepanium) hexachlorostannate(IV) dichloride (1) and tetrakis(azepanium) hexabromostannate(IV) dibromide (2) crystals have been grown after slow evaporation of the solvent and characterized through single-crys

Full text of DOI:10.1016/j.molstruc.2020.129515

Journal Pre-proof
Synthesis, structure, third-order nonlinear optical properties and
Hirshfeld surface analysis of tetrakis(azepanium)
hexachlorostannate(IV) dichloride and tetrakis(azepanium)
hexabromostannate(IV) dibromide
M. Manonmani , C. Balakrishnan , M. Dhanalakshmi ,
S. Rafi Ahamed , G. Vinitha , R.M. Sockalingam
PII:
S0022-2860(20)31830-5
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.129515
MOLSTR 129515
To appear in:
Journal of Molecular Structure
Received date:
Revised date:
Accepted date:
5 June 2020
21 October 2020
24 October 2020
Please cite this article as: M. Manonmani , C. Balakrishnan , M. Dhanalakshmi , S. Rafi Ahamed ,
G. Vinitha , R.M. Sockalingam , Synthesis, structure, third-order nonlinear optical properties
and Hirshfeld surface analysis of tetrakis(azepanium) hexachlorostannate(IV) dichloride and
tetrakis(azepanium) hexabromostannate(IV) dibromide, Journal of Molecular Structure (2020), doi:
https://doi.org/10.1016/j.molstruc.2020.129515
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Highlights
• The compounds (1) and (2) are isostructural with small variations in lattice
parameters.
• The band gap energies of the hybrids can be easily tuned by altering the halide
ion.
• Both the hybrids possess a significant third-order nonlinear response.
• Intermolecular interactions are analyzed and quantified by 2D fingerprint plots via
Hirshfeld surface analysis.

Synthesis, structure, third-order nonlinear optical properties and Hirshfeld
surface analysis of tetrakis(azepanium) hexachlorostannate(IV) dichloride
and tetrakis(azepanium) hexabromostannate(IV) dibromide
M. Manonmania, C. Balakrishnana, M. Dhanalakshmia, S. Rafi Ahamedb, G. Vinithac,
RM. Sockalingama*
a Crystal Growth Lab, Department of Chemistry, Annamalai University, Annamalainagar, Tamil Nadu, India
b Department of Physics, Academy of Maritime Education and Training, deemed to be University, Chennai, Tamil Nadu
c Division of Physics, School of Advanced Science, VIT Chennai, Chennai, Tamil Nadu, India
Abstract
The new organic-inorganic hybrids of tetrakis(azepanium) hexachlorostannate(IV)
dichloride (1) and tetrakis(azepanium) hexabromostannate(IV) dibromide (2) crystals have
been grown after slow evaporation of the solvent and characterized through single-crystal X-
ray diffraction analysis. The characteristic functional groups present in the compounds are
confirmed by FT-IR analysis. The direct band gap values for the compounds are estimated by
the application of Kubelka-Munk function. Photoluminescence studies exhibit fluorescent
emission of both the compounds in the solid-state at room temperature. TG/DTA analysis
reveals the thermal pattern of the compounds. Bond valence sum (BVS) calculation
confirmed the formal oxidation state of tin to be +4. Z-scan studies very much reveal that
both the compounds exhibit significant third-order nonlinear optical response. Investigation
of the intermolecular interactions and crystal packing using Hirshfeld surface analysis,
derived by single-crystal XRD data, reveals the close contacts associated with strong
interactions.
Keywords: Organic-inorganic hybrids; Hirshfeld surface; Z-scan studies; Band gap; Thermal
pattern

1. Introduction
Hybrid materials are being used to systems such as metal-organic frameworks, highly
ordered polymers, sol-gel compounds and macro-structured inorganic particles in the organic
matrix [1]. Perovskites belong to a class of inorganic crystals with general chemical formula
ABX3 composition can be constructed with various metal cations (A and B) and anions (X).
In such a perovskite structure, the inorganic cations A and B are coordinated by 12
(cuboctahedral) and 6 (octahedral) anions X, respectively. The discovery is credited to
Gustav Rose following his report on the oxide perovskite calcium titanate (CaTiO3) in 1839
[2]. Any material that adopts the same crystal structure as isostructural to CaTiO3, namely,
ABX3 structure [3], where ‘A’ site is occupied by an organic ammonium cation and the ‘B’
site by metal ion such as Sn2+, Pb2+, Ge2+, etc., while the X site is occupied by a halide anion
Fˉ, Clˉ, Brˉand Iˉ is a hybrid perovskite [4,5]. Very recently, organic-inorganic hybrid
perovskites have attracted considerable attraction in a broad variety of materials, including
data storage [6], ferroelectrics [7], superconductors [8], light-emitting devices [9], ionic
conductors [10], solar cells [11] and nonlinear optical (NLO) materials [12].
NLO effects are extensively leveraged in optoelectronic fields such as saturable
absorbers, switches and harmonic generators. In remarkable, third-order nonlinear materials
have been designed and evolved to be applicable in a class of applications [13]. The
exploration for new materials that illustrate large nonlinear optical properties remains
strongly motivated both by the potential applications as well as the basic knowledge of
photophysics that can be derived from correlations in chemical structure and nonlinear
signals. General strategies for improving the third-order nonlinear susceptibility are
manipulate conjugated organic molecules with highly delocalized electrons and/or push-pull
nature [14], semiconductor-doped glasses with resonant enhancement [15] and metal halide
perovskite films [16].
The crystal structures of bis(organic ammonium cations) with hexahalostannate(IV)
[17-29] and tetrakis(organic ammonium cations) with hexachloridostannate(IV) dichlorides

[30-33] have been described. Here, we report the investigation of structural characterization,
optical and third-order nonlinear optical responses of tetrakis(azepanium)
hexachlorostannate(IV) dichloride (1), and tetrakis(azepanium) hexabromostannate(IV)
dibromide (2) hybrid perovskites. Molecular interactions are quantified by fingerprint plots
derived from Hirshfeld surfaces.
2. Experimental
2.1 Synthesis and crystal growth
Preparation of tetrakis(azepanium) hexachlorostannate(IV) dichloride (1)
Azepane (4 mM) and hydrochloric acid (3 mL) in ether were mixed at room
temperature to obtain azepanium chloride precursor solution. Tin(IV) chloride was prepared
by dissolving tin shots (0.118 g, 1 mM) in 5mL hydrochloric acid at room temperature (6 h).
To the freshly prepared ethanolic solution of azepanium chloride precursor solution, tin(IV)
chloride was added with constant stirring (Scheme 1). Colourless crystals were formed from
the solution after 14-16 d. Photograph of as-grown crystals picturized in Fig. 1.
Preparation of tetrakis(azepanium) hexabromostannate(IV) dibromide (2)
Azepane (4 mM) and hydrobromic acid (3 mL) in ether were mixed at room
temperature to obtain azepanium bromide precursor solution. Tin(IV) bromide was prepared
by dissolving tin shots (0.118 g, 1 mM) in 5mL hydrobromic acid at room temperature (6 h).
To the freshly prepared ethanolic solution of azepanium bromide precursor solution, tin(IV)
bromide was added with constant stirring (Scheme 2). Crystals of the compound (2) suitable
for X-ray analysis were grown from the saturated ethanolic solution after 14-16 d.
Photograph of as-grown crystals picturized in Fig. 1.
)

2.2. Characterization techniques
FT-IR spectra were recorded using Shimadzu IR Affinity-1 FT-IR spectrophotometer
as KBr discs. A Bruker AXS kappa apex3 CMOS X-ray diffractometer was used for single
crystal XRD studies. Data were collected on a diffraction system which employs graphite
monochromated MoK radiation ( = 0.71073 Å). The structures were solved and refined by
full-matrix least squares on F2 with WinGX software package utilizing SHELXT-2014/7 and
shelx SHELXL version number 2014/7 and 2018/3. The UV– Diffuse Reflectance Spectra
was recorded using Shimadzu UV2600 UV-Vis spectrophotometer. Photoluminescence
spectrum was recorded by HJY:Fluorolg F3-111 Fluorescence spectrometer. In the Z-scan
experiment, the samples were excited by continuous wave (CW) (532 nm, 50 mW) and
ultrafast (800 nm, 150 fs) lasers. In CW excitation Gaussian profile from diode pumped
Nd:YAG laser beam was focused on a 1 mm cuvette by the lens of focal length 3.5 cm to
produce a beam waist (ω0) of 15.35 mm. Thermogravimetric (TG) and differential thermal
analysis (DTA) were carried out using a NETZSCH STA 449 F3 thermal analyzer using
nitrogen atmosphere.
3. Results and discussion
3.1 FT-IR
The vibrational spectra of (1) and (2) are represented in Fig. S1. The bands perceived
at 3424 and 3436 cm–1 for compound (1) and (2) respectively, which corresponds to the
asymmetric stretching vibrations of NH2 group. The sharp peak observed at 3155 and
3150 cm-1 corresponds to the symmetric stretching vibrations of NH2 group for compound (1)
and (2) respectively. The NH bending vibrations are perceived at 1575 and 1580 cm–1. The
C-H stretching vibrations observed at 2935 and 2940 cm-1. The bands at 1350 and 1370 cm–1
are due to the stretching modes of C–N moiety [34]. The rocking vibrations of the CH2 are
observed at 880 and 878 cm–1 for compounds (1) and (2) respectively.

3.2. Single-crystal X-ray structure analysis
Single crystals of tetrakis(azepanium) hexachlorostannate(IV) dichloride (1) and
tetrakis(azepanium) hexabromostannate(IV) dibromide (2) suitable for X-ray analysis were
collected by slow evaporation of ethanolic solutions of the reaction mixture at room
temperature. Crystal data, data collection refinement parameters and the results of the
analyses of compounds are exhibited in Table 1. Bond lengths, bond angles and dihedral
angles are listed in Tables S1-S3. Both the compounds crystallize in the monoclinic system,
with a centrosymmetric space group C2/m.
The Oak Ridge Thermal-Ellipsoid Plot (ORTEP) and molecular packing diagram of
(1) are exhibited in Fig. 2. The compound (1) consists of four azepanium cations, two
chloride anions and one independent octahedral [SnCl6]2- anion. The crystal structure consists
of alternating organic and inorganic layers extending parallel arrangement is demonstrated in
Fig. 3a. Sn–Cl bond distances range from 2.4192(9) – 2.4561(3) Å and Cl–Sn–Cl bond angles
vary from 89.24(5) - 90.76(5)°. The compound shows extensive hydrogen-bonded
interactions. The Sn atom is six-coordinated and forms a quasi-regular octahedral
arrangement [35]. The octahedral environmental parameters of compound (1) is listed in
Table 2. The effective coordination number is 5.9896 and bond length distortion index is
0.00674. The bond distances are similar to those found in other octahedral Sn(IV) compounds
[33]. The crystal packing in (1) is controlled by the classical hydrogen bond, in extension to
coulombic forces. In this system, azepanium cations interact with chloride anions and
[SnCl6]2- octahedra via N-H•••Cl and C-H•••Cl hydrogen bonds. The inter- and intramolecular
hydrogen bonds with hexachlorostannate(IV) and azepane are listed in Table 3a. Fig. 3b
shows the N(1A) atom involves three-centre hydrogen bonding with three Cl atoms
N(1A^c)•••Cl(1), N(1A^c)•••Cl(2)#2 and N(1A^c)•••Cl(1)#1 with the corresponding distances
are 3.432(19) Å, 3.364(3) Å and 3.432(19) Å respectively.

The ORTEP and molecular packing diagram of (2) are exposed in Fig. 2. The
compound (2) also consists of four azepanium cations, two bromide anions and one
independent octahedral [SnBr6]2- anion. The crystal structure consists of alternating organic
and inorganic layers extending parallel arrangement and is demonstrated in Fig. 4a. Sn–Br
bond distances range from 2.5868(9) – 2.6288(13) Å and Br–Sn–Br bond angles vary from
89.39(4)-90.61(4)°. The compound shows extensive hydrogen-bonded interactions. The Sn
atom is six-coordinated and forms a quasi-regular octahedral arrangement. The octahedral
environmental parameters of compound (2) is listed in Table 2. The effective coordination
number is 5.9882 with bond length distortion index 0.00718 and bond angle variance 0.3827°
(Table 2). In this compound, azepanium cations interact with bromide anions and [SnBr6]2-
octahedra via N-H•••Br and C-H•••Br hydrogen bonds. The inter- and intramolecular hydrogen
bonds with hexabromostannate(IV) and azepane are listed in Table 3b. Atoms C(4), N(1) and
N(2) participate in the formation of strong/weak inter- and intramolecular hydrogen bonds
with Br atoms of [SnBr6]2- octahedron. Fig. 4b shows the N(1) involves three-centre
hydrogen bonding with three Br atoms N(1)-H(1B^a)•••Br(1), N(1)-H(1B^b)•••Br(2) and
N(1)-H(1B^c)•••Br(1) with the corresponding distances are 3.569 Å, 3.525 Å and 3.569 Å
respectively (Table 3b). Compounds (1) and (2) are isostructural with small variations in
lattice parameters. Various geometries associated with molecules have been described as
‘slightly distorted’ or severely distorted’ polyhedron. The extent of distortion of a particular
molecular structure from an ideal polyhedron can be assessed by symmetry measures. Table 2
listed values indicate the fact that both the compounds are of distorted octahedral geometry.
3.3. Bond valence sum analysis
Bond valence sum (BVS) analysis is used to determine the valence of the central atom
from the experimentally derived bond distances [36]. BVS estimations are carried out based
on the bond distances obtained from the single-crystal X-ray structural analysis. Hence, BVS

studies indirectly prove the correctness of the crystal structures determined [37]. The method
depends on the Rij value for an i–j bond which is primarily ionic [38,39]. In a compound, the
oxidation state of a central atom ‘i’ bonded to ‘j’ match up to the bond valence, V and the
total valence of the central atom is its oxidation state,
V = Σvij= exp[(Ro–Rij)/b]
where Ro is used as reported for a large number of ionic compounds [40] and Rij is the
experimentally determined bond distance. The constant b can be assumed to be 0.37 [41].
Bond valence sums of (1) and (2) are 3.95 and 3.93 respectively (Table 4), which proved the
formal oxidation state of tin as 4+ unequivocally.
3.4. Hirshfeld surface analysis
Hirshfeld surface analysis and fingerprint plots were generated from the crystal data
were carried out with the TONTO incorporated CrystalExplorer 3.1 program. A three-
dimensional view of the molecular Hirshfeld surfaces [42,43] of compounds (1) and (2) are
revealed in Fig. 5 shows surfaces that have been mapped over dnorm, de, di and shape index.
Distances from the Hirshfeld surface to the nearest nucleus inside the surface (di) and outside
the surface (de) were the first functions of distance explored for mapping on the surfaces. The
red colour circular spots indicated as close contacts, through green to blue colour indicates
long contacts and the normalized contact distance, well-defined in terms of de, di and the van
der Waals radii of the atoms. Shape index is defined as the local shape topography of the 3D
surface.
The fingerprint plots [44] of (1) and (2) have spread this 2D graph as a griddle of
coloured areas, over the range 0.4–3.0 Å in each of di and de. Bonding interactions are
quantified for the compounds (1) and (2) are, (1): H•••Cl (14.5%), Cl•••H (18.3%) and H•••H
(67.2%). (2): H•••Br (16.0%), Br•••H (21.5%) and H•••H (62.5%) shown in 2D fingerprint plot

(Fig. 6). The Cl•••H/Br•••H interactions are characterized by a spike in the bottom area
whereas the H•••Cl/H•••Br interactions are indicated by a spike in the upper region in the
fingerprint plot. The H•••H interactions are marked in the middle spike of fingerprint plot.
Leading interactions hold more space in the fingerprint region.
3.5. Diffuse reflectance spectroscopy
Diffuse reflectance spectra of (1) and (2) are shown in Fig. 7. The reflectance
increased above 270 nm for (1) and 400 nm for (2). The absorption below 450 nm is of
organic origin in the hybrids. The band gap was determined to be 4.23 eV and 2.98 eV for (1)
and (2) respectively, using a plot of (F(R)hυ)2 versus (hυ) as shown in inset Fig. 7. The bromo
hybrids show a lower band gap compared to chloro hybrids because of the orbital
contribution to the top of the valance band [45]. Therefore, the band gaps associated with
these hybrids can be easily tuned by altering the halide ion.
3.6. Photoluminescence spectral studies
On excitation of (1) and (2) with 277 nm and 404 nm radiations respectively, the
compounds exhibited emission bands as shown in Fig. 8. The maxima appeared at 402 nm for
(1) and 519 nm for (2). Relatively low full-width half-maximum associated with (2) indicates
better quality of epilayer present in this compound than in (1). Besides, the proximity of
emission maxima of the compounds (1) (402 nm) as well as (2) (519) shows the identical
nature of the photoluminescence process responsible for the emission [46].
3.7. Z-scan studies
The nonlinear absorption (β), nonlinear refractive index (n2), and third-order nonlinear
susceptibility (χ(3)) were defined by standard equations [47,48]. The NLO properties of the
hybrids (1) and (2) were experimented by the Z-scan technique. Here the open and closed

aperture Z- scan curves are used for β and n2 measurements and this method has been broadly
accepted by NLO society due to their high sensitivity and simplicity. The maximum energy
density of the beam is at the focus, which is being symmetrically minimized both sides for
the positive and negative values of z, this leads to the difference in laser intensity at different
z positions. The transmittance intensity variations corresponding to the z values, the closed
and open aperture z-scan curve can be represented. The recorded normalized transmittance
for two compounds is revealed in Fig. 9.
The peak followed by a valley normalized transmittance curve obtained under the
closed aperture configuration shows the characteristic self-defocusing behaviour [49,50]. The
positive nonlinear absorption has been seen in all the compounds due to strong reverse
saturable absorption in these materials. Third-order NLO parameters are list out in Table 5.
The χ(3) values of common materials lie in the range 10-12 to 10-5 esu [51-55] and a
comparison (Table 6) reveals that (1) and (2) possess a significant third-order nonlinear
response and hence promising NLO candidate. Largest value of χ(3) and hence significantly
perceived nonlinearity could be associated with intra- and intermolecular hydrogen bonds.
3.8. Thermal analysis
Thermogravimetric analysis (TGA) was carried out under a nitrogen atmosphere at a
heating rate of 20 K min–1 in the temperature range of 35–1100°C. Thermal behaviour of (1)
and (2) are exposed in Fig. 10 and the data are listed in Table 7. Compound (1) is stable up to
238°C. The first weight loss of 67.3% (calcd.: 67.6%) in the range of 240–397°C, due to the
loss of four molecules of azepanium chloride. The second weight loss is due to the loss of
two molecules of chlorine in the temperature range: 398–498°C. The final residue containing
tin metal evaporated slowly above 499°C.

In compound (2), the first weight loss of 61.9% (calcd.: 62.2%) in the range of 245–
402°C, corresponds to the loss of four molecules of azepanium bromide. The second weight
loss is due to the loss of two molecules of bromine in the temperature range: 403-513°C. The
final residue containing tin metal evaporated slowly above 514°C. In both the compounds, all
the three processes are exothermic nature as is evident from the differential thermal analysis
(DTA) curves (Fig. 10). TG–DTA curves confirmed the suggested formulae of the
compound.
4. Conclusions
Organic-inorganic hybrids such as tetrakis(azepanium) hexachlorostannate(IV)
dichloride (1) and tetrakis(azepanium) hexabromostannate(IV) dibromide (2) have been
synthesized and characterized by single-crystal X-ray diffraction techniques. IR spectral
analysis of the compounds shows that different vibrational bands of the organic moiety show
very little change on hybrid formation with tin. Diffuse reflectance spectral analysis showed
the band gap of the chloride hybrids to be larger than the bromide analogue. Therefore, by
changing the halide ion it is possible to tune the band gap of the hybrid material. Single
crystal X-ray structural analysis showed the octahedral nature of the hexahalo dianions. Both
tetrakis(azepanium) hexachlorostannate(IV) dichloride (1) and tetrakis(azepanium)
hexabromostannate(IV) dibromide (2) crystallize in monoclinic crystal system and are
isostructural with the space group C2/m. Azepanium cations capped the central hexahalo
2–
anion in the unit cell. The SnX6 ions indicated their distorted octahedral geometry. BVS
analysis established the formal oxidation state of tin as 4+.
CRediT author statement
M. Manonmani: Methodology, Investigation and Formal analysis, C. Balakrishnan: Writing –
original draft, M. Dhanalakshmi: Software and Formal analysis, S. Rafi Ahamed: Formal

analysis, G. Vinitha: Formal analysis, RM. Sockalingam: Conceptualization, Supervision,
Writing- Reviewing and Editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
Acknowledgements
The authors thank DST PURSE Phase-II, Annamalai University and also thank SAIF,
IIT Madras, Chennai, for providing single-crystal XRD facility.
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Table 1.
Crystal data and structure refinement for (1) and (2)
(1)
(2)
C24H56Br8N4Sn
Empirical formula
Formula weight g/mol
Temperature
C24H56Cl8N4Sn
803.01
1158.67
296(2) K
301(2) K
0.71073 Å
Monoclinic
C2/m
Wavelength
0.71073 Å
Monoclinic
C2/m
Crystal system
Space group
Unit cell dimensions
a = 16.6981(10) Å
b = 10.8131(6) Å
c = 12.9044(8) Å
1861.55(19) Å3
2
α = 90°
17.182(6) Å
90°
β = 126.97(10)° 10.993(5) Å
125.993(11)°
90°
γ = 90°
13.098(4) Å
2001.7(13) Å3
2
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
1.433 Mg/m3
1.281 mm-1
828
1.922 Mg/m3
8.642 mm-1
1116
Crystal size
0.150 x 0.150 x 0.100 mm3
0.230 x 0.280 x 0.310 mm3
3.55 to 30.04°
Theta range for data collection 3.054 to 30.536°
-24<=h<=24, -12<=k<=15,
-18<=l<=15
Index ranges
-20<=h<=23, -15<=k<=15, -18<=l<=18
Reflections collected
20224
8091
Independent reflections
Data / restraints / parameters
Goodness-of-fit on F2
2937 [R(int) = 0.0544]
2937 / 204 / 161
1.292
2994 [R(int) = 0.0600]
2994 / 0 / 92
1.067

Absorption correction
Max. and min. transmission
Refinement method
Final R indices [I>2sigma(I)]
R indices (all data)
Semi-empirical from equivalents
0.7461 and 0.5791
Semi-empirical from equivalents
0.7460 and 0.2994
Full-matrix least-squares on F2
R1 = 0.0511, wR2 = 0.1135
R1 = 0.0670, wR2 = 0.1321
n/a
Full-matrix least-squares on F2
R1 = 0.0537, wR2 = 0.1489
R1 = 0.0757, wR2 = 0.1613
n/a
Extinction coefficient
Largest diff. peak and hole
CCDC
1.065 and -1.195 e.Å-3
1992840
1.110 and -1.593 e.Å-3
1992842
Table 2.
parameters for compounds (1) and (2)
(1)
Bond distances
2.4192(9) Å
2.4192(9) Å
2.4561(3) Å
2.4561(3) Å
2.4192(9) Å
2.4192(9) Å
2.4315
(2)
Bond distances
Sn1-Cl1
Sn1-Br1
2.5868(9) Å
2.5868(9) Å
2.6288(13) Å
2.5868(9) Å
2.6288(13) Å
2.5868(9) Å
2.6008
Sn1-Cl1i
Sn1-Br1i
Sn1-Br2
Sn1-Br1ii
Sn1-Br2i
Sn1-Br1iii
Sn1-Cl2
Sn1-Cl2i
Sn1-Cl1ii
Sn1-Cl1iii
Average bond length (Å)
Polyhedral volume (Å3)
Distortion index (bond length)
Quadratic elongation
Bond angle variance (deg.^2)
Effective coordination number
19.1617
23.4499
0.00674
0.00718
1.0003
1.0002
0.5377
0.3827
5.9896
5.9882

Table 3a. Hydrogen bonds for (1) [Å and °]
D-H•••A
d(D-H)
d(H•••A)
2.92
d(D•••A)
3.861(16)
3.098(9)
3.170(11)
3.11(3)
<(DHA)
164.3
150.1
176
C(4A^a)-H(4A1^a)•••Cl(1)
N(2A^a)-H(2A1^a)•••Cl(3)
N(2A^a)-H(2A2^a)•••Cl(3)#3
N(1A^c)-H(1A3^c)•••Cl(3)
N(1A^c)-H(1A4^c)•••Cl(1)
N(1A^c)-H(1A4^c)•••Cl(1)#1
N(1A^c)-H(1A4^c)•••Cl(2)#2
0.97
0.89
0.89
0.89
0.89
0.89
0.89
2.29
2.28
2.23
173.7
132.1
132.1
136.9
2.77
3.432(19)
3.432(19)
3.364(3)
2.77
2.66
Symmetry transformations used to generate equivalent atoms:
#1 x,-y+1,z #2 -x+1,-y+1,-z #3 -x,-y+1,-z-1
Table 3b.
Hydrogen bonds for (2) [Å and °]
D-H•••A
d(D-H)
0.97
0.97
0.89
0.89
0.89
0.89
0.89
d(H•••A)
3.02
d(D•••A)
3.901
3.901
3.250
3.250
3.569
3.525
3.569
<(DHA)
151.9
151.9
132.5
177.1
127.3
143.0
127.3
C(4)-H(6B^a)•••Br(1)
C(4)-H(6B^b)•••Br(1)
N(2)-H(2B^a)•••Br(3)
N(1)-H(1A^a)•••Br(3)
N(1)-H(1B^a)•••Br(1)
N(1)-H(1B^b)•••Br(2)
N(1)-H(1B^c)•••Br(1)
3.02
2.58
2.36
2.96
2.77
2.96
Symmetry transformations used to generate equivalent atoms:

Table 4.
Bond valence sum calculation of compounds (1) and (2)
Compound
Co. No.
6
Bond distances (Å)
V = Σvij
Sn1-Cl1
Sn1-Cl1i
Sn1-Cl1ii
Sn1-Cl1iii
Sn1-Cl2
Sn1-Cl2i
(1)
3.95*
2.4192(9)
Sn1-Br1
2.5868(8)
2.4192(9)
Sn1-Br1i
2.5868(8)
2.4192(9)
Sn1-Br2
2.6288(9)
2.4192(9)
Sn1-Br1ii
2.5868(8)
2.4561(13)
Sn1-Br1iii
2.5868(8)
2.4561(13)
Sn1-Br2i
2.6288(9)
(2)
6
3.93*
* Values rounded off
Table 5.
Third-order NLO parameters of (1) and (2)
Calculated values
(1) (2)
Third-order NLO Parameters
Nonlinear refractive index (n2) (cm2/W)
6.17 × 10-10
2.82 × 10-5
2.11 × 10-7
4.37 × 10-7
2.35 ×10-9
9.70 ×10-5
1.91 ×10-6
2.08 ×10-7
Nonlinear absorption coefficient (β) (cm/W)
Real part of the third-order susceptibility [Re(χ3)] (esu)
Imaginary part of the third-order susceptibility [Im(χ(3))] (esu)

Third-order nonlinear optical susceptibility (χ(3)) (esu)
4.85 × 10-7
1.92 ×10-6
Table 6.
Comparison of third-order nonlinear susceptibility (χ(3)) of some perovskite materials
Specimen
χ(3) (esu)
1.7 x 10-5
Ref
[52]
LiNbO3
ZnWO4
2.32 × 10-6
1.6 × 10-6
4.3 × 10-10
9.5 × 10-10
4.85 × 10-7
1.92 × 10-6
[53]
CH3NH3PbBr3
CsPbBr3 nanocubes
CsPbBr3 nanorods
(1)
[54]
[55]
[55]
Present work
Present work
(2)
Table 7.
Mass losses in compounds (1) and (2)
Decomp. range
Mass loss (%)
67.3 (calcd.: 67.6)
Fragment lost
(°C)
240 –397
398-498
> 499
4(C6H14NCl)
4Cl
C24H56Cl8N4Sn (1)
17.6 (calcd.: 17.7)
14.8 (calcd.: 14.8)
Residual Sn

evaporation
4(C6H14NBr)
4Br
61.9 (calcd.: 62.2)
27.5 (calcd.: 27.6)
245 –402
403–513
C24H56Br8N4Sn (2)
Residual Sn
evaporation
10.2 (calcd.: 10.2)
> 514
Figure Captions
Fig. 1. Photographs of as-grown crystals (1) and (2)

Fig. 2. (a) ORTEP and (b) packing diagram of (1) and (2) (hydrogen bonds as blue dashed lines)

Fig. 3. (a) Diagram of the layered packing and octahedra viewed along the a-axis and (b)
hydrogen-bonding network for compound (1) (most of the hydrogens are omitted for
clarity)

Fig. 4. (a) Diagram of the layered packing and octahedra viewed along the a-axis and (b)
hydrogen-bonding network for compound (2) (most of the hydrogens are omitted for
clarity)\

Fig. 5. Hirshfeld surface analysis of (1) and (2) (a) dnorm (b) de (c) di and (d) shape index

Fig. 6. Fingerprint plots of (1) and (2)

Fig. 7. UV spectra (Tauc plot is given as an inset) of (1) and (2)

Fig. 8. PL spectra of compounds (1) and (2) solid-state at room temperature
Fig. 9. Closed and open aperture Z-scan curves of (1) and (2)