Accepted Manuscript

Synthesis, growth and characterization of a new metal-organic NLO material:

Dibromo bis (L-proline) Cd (II)

K. Boopathi, P. Ramasamy

PII: S0022-2860(14)00981-8

DOI: http://dx.doi.org/10.1016/j.molstruc.2014.09.067

Reference: MOLSTR 20975

To appear in: Journal of Molecular Structure

Received Date: 13 August 2014

Revised Date: 22 September 2014

Accepted Date: 22 September 2014

Please cite this article as: K. Boopathi, P. Ramasamy, Synthesis, growth and characterization of a new metal-organic

NLO material: Dibromo bis (L-proline) Cd (II), Journal of Molecular Structure (2014), doi: http://dx.doi.org/

10.1016/j.molstruc.2014.09.067

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1

Synthesis, growth and characterization of a new metal-organic NLO material:

Dibromo bis (L-proline) Cd (II)

K. Boopathi, P. Ramasamy*

Centre for Crystal Growth, SSN College of Engineering, Kalavakkam-603110, India.

Abstract

Single crystals of metal-organic complex dibromo bis (L-proline) Cd (II) (DBPC)

were grown by low temperature solution growth method. The synthesized material was

purified by the process of repeated recrystallization. The grown crystal was confirmed by

Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (1H NMR and 13C NMR)

spectral studies and single crystal X-ray diffraction. Single crystal X-ray analysis shows that

DBPC crystallizes in orthorhombic crystal system with space group P212121. The

coordination geometry around the cadmium (II) center is distorted tetrahedral. The title

compound was characterized by UV-Vis-NIR study shows that the crystal is transparent in

the wavelength range 200-1100 nm and TG/DTA analysis. The magnetic property of DBPC

is investigated at room temperature. The microhardness test was carried out. The second

harmonic efficiency of powdered DBPC was determined by Kurtz and Perry method and it is

2.25 times that of KDP

Key words: Chemical synthesis, Crystal structure, Growth from solutions, Optical properties, Magnetic materials, Nonlinear optical material

*Corresponding author

Phone: +91-9283105760, +914427475166

Email: proframasamy@hotmail.com; ramasamyp@ssn.edu.in

2

1. Introduction

In the last several decades, Non-Linear Optical (NLO) materials have attracted much

attention due to their potential uses in many fields, such as optical modulation, optical

switching, optical logic, frequency shifting, colour displays and optical data storage for the

developing technologies in telecommunication and in efficient signal processing [1–5].

Among various second order NLO materials, metal-organic coordination compounds have

attracted much more attention due to their capability of combining the advantage of both

organic and inorganic materials, such as high NLO coefficients, stable physico-chemical

properties and better mechanical intension [6–8]. NLO material capable of frequency

conversion is generally composed of an electron donor (D), an acceptor (A) and a conjugate

π -system as a bridge providing the electronic communication between the donor and

acceptor [9]. And for the second order NLO materials, the bridged system units must be

packed in a non-centrosymmetric way. In metal-organic compounds, metal centers can act as

both donors and the bridging moiety in D–π–A system, and the metal–ligand bond is

expected to display large molecular hyperpolarisability because of the transfer of electron

density between the metal atom and the conjugated ligand system [10]. Furthermore, in the

case of metal-organic coordination complex, the group IIB divalent d10ions, Zn2+, Cd2+, and

Hg2+ complexes have attracted our interest for their unique characteristics of pale colour and

high thermal stability.

Amino acids have two or more types of coordination atoms and can act as various

bridging ligands [11–13]. Taking advantage of the properties of the amino acid ligands, an

amino acid complex was used as a ligand in order to synthesize a new heteronuclear complex.

One of the continuing challenges in materials chemistry concerns the elucidation of structure

property relationships [14, 15]. This is especially true with second-order nonlinear optical,

i.e., SHG, materials [16].

3

L- Proline is an abundant amino acid in collagen and is exceptional among the amino

acids because it is the only one in which the amine group is part of a pyrrolidine ring, thus

making it rigid and directional in biological systems [17]. L-Proline has been exploited for

the formation of salts with different organic and inorganic compounds [18]. Single crystal of

l-proline shows no centre of symmetry and its NLO coefficients have been examined by

Boomadevi and Dhanasekaran [19]. Kandasamy et al., [20] have grown L-PCCM and

reported that the second harmonic generation efficiency of their crystal was twice that of

KDP. As metal atoms or ions occur widely in association with proteins and show a variety of

functions, one can expect that synthesizing the amino acid complexes with metal salts and

characterizing them would yield useful and informative results [21, 22]. In the present

communication, we report on the synthesis, crystal growth, and spectral characterization of

metal organic NLO crystal dibromo bis (L-proline) Cd (II) from aqueous solution by slow

evaporation method for the first time.

2. Experimental section

2.1. Materials synthesis, crystal growth

The starting material of L-proline and CdBr2 was taken in 2:1 stoichiometric ratio to

synthesise dibromo bis (l-proline) Cd (II). The reaction scheme is shown in Fig.1. The

calculated amount of cadmium bromide was first dissolved in deionized water.

L-proline was then added to the solution slowly by stirring. The prepared solution was

allowed to dry at room temperature and the salt was obtained by slow evaporation technique.

The purity of the synthesized salt was improved by successfully recrystallization. After 25

days of growth, transparent single crystal of dimension 12mm×9mm×4 mm was obtained by

slow evaporation technique. The as grown crystals are shown in Fig.2. The crystal had good

compositional stability and showed no degradation when stored in the open air for several

months.

4

3. Results and discussion

3.1. Spectroscopic studies

The FT-IR spectrum of (DBPC) is recorded using a JASCO FT-IR 410 spectrometer

by the KBr pellet method. The vibrational spectroscopy provides evidence for the charge

transfer interaction between the donor and acceptor groups through π-electron movement.

The intra molecular hydrogen bonding network is formed between amino hydrogen’s of

dibromo bis (L-proline) Cd (II) atoms. The FT-IR spectrum (Fig. 3) shows the strong peak at

3028 cm-1 due to N+-H stretching frequency. The strong peak at 1633 cm-1 and 1552 cm-1 can

be assigned to the C=O stretching of asymmetric and symmetric vibrations of COO- groups.

The peak at 1331 cm-1 is assigned to the NH2+ wagging. The peaks observed between

2732 -3028 cm-1 are the characteristic of L-Proline. The wagging and rocking of CH2 is

1331 cm-1 and 840 cm-1. The peak at 1050 cm-1 is assigned to the C-N stretching vibrations.

The NMR spectral analysis is the important analytical technique used to the study of

the structure of organic compounds. The 1H and 13C NMR spectrum of DBPC was recorded

using D2O as solvent on a Bruker 300MHz (Ultra shield) TM instrument at 23 °C (300 MHz

for 1H NMR and 75 MHz for 13C NMR) to confirm the molecular structure. In the present

investigation, the 1H and 13C NMR spectra were recorded to confirm the molecular structure.

The proton NMR spectrum is shown in Fig.4 (a). In proton NMR spectrum, the CH2 (a)

proton appears as a multiplet centred at δ 1.64 ppm in the aliphatic region of the spectrum.

The multiplet protons signal appearing at δ 1.95 ppm has been assigned for the CH2 (b)

protons. The signal corresponding to CH2 (c) protons of the pyrrolidine ring is appearing as a

triplet centred at δ 2.80 ppm. The signal due to CH2 (d) protons is shifted to higher δ values

as a consequence of the electron withdrawing carbonyl group in the vicinity and appears as a

triplet at δ 4.08 ppm. The sharp singlet around δ 4.7 ppm is attributed to the presence of D2O.

The 13C chemical shift appearing at δ174 ppm confirms the presence of carboxylate

5

functional group in L-Proline (COO-) and the presence of aliphatic carbon chemical shift is at

δ 23.82, 29.00 ppm and 46.00 ppm (CH2). The conformation of another aliphatic carbon

appears at δ 61 ppm (CH). The 13C spectrum is shown in Fig.4 (b).

3.2. Single crystal X-ray diffraction

The single crystal X-ray diffraction studies of DBPC were performed using Bruker

AXS Kappa APEX II CCD Diffractometer equipped with graphite monochromated Mo Kα

radiation (λ=0.71073 Å) at room temperature. The single crystal of size 0.3 x 0.2 x 0.25 mm3

was used for the study. Accurate unit cell parameters were determined from the reflections of

36 frames measured in three different crystallographic zones by the method of difference

vectors. Data collection, data reduction and absorption correction were performed by APEX2,

SAINT-plus and SADABS programs [23]. The crystallographic data and the refinement

details for DBPC are summarized in Table .1. A total of 8771 reflections were recorded

with 2θ range 2.32 º to 28.79 º of which 3065 reflections are considered as unique reflections

with I > 2σ(I). The structure was solved by direct methods procedure using SHELXS-97

program and refined by Full-matrix least squares procedure on F2 using SHELXL-97

program [24]. The final refinement converges to R-values of R1= 0.0210 and WR2 = 0.0434.

Complex DBPC crystallizes in orthorhombic crystal system with P212121 space

group. The complex has a very similar structure to that of CdCl2 (Hpro); it consists of a one

dimensional polymer bridged by bromine atoms and carboxyl oxygen atoms. The Cd (II)

coordinates with two bromine atoms and two carboxyl oxygen atoms of two L-Proline

ligands: each of them is zwitter ionic. The carbon atom C4 of the pyrrolidine ring is

disordered over two positions with site occupancies of 0.546(7) and 0.454(7) respectively.

The coordination environment around the Cd atom, involving Br atoms and carboxyl

O atoms, may be visualized as a distorted tetrahedral as shown in the ORTEP view (Fig. 5).

The coordination of two bromine atoms with cadmium are of different bond length Cd (1)-Br

6

(2) [2.6051(4) A°], Cd (1)-Br (1) [2.5345(5) A°]. These are due to torsion bending of

pyrrolidine ring. The carboxylate groups in compound DBPC are not planar with the

pyrrolidine ring as shown in the torsion angle of O(2)-C(1)-O(1)-Cd(1), O(4)-C(6)-O(3)-

Cd(1), which are -18.5(5)º, 8.2 (4)º respectively. The packing arrangement of the molecule

viewed down in the c-axis is shown in Fig.6. The metal ligand coordination and molecular

geometry are similar to that observed in related amino acid containing compounds [11-13].

The selected bond lengths and angles of DBPC are listed in Table.2. and Table .3.

The hydrogen bond is the most important of all directional intermolecular

interactions. The corresponding data for the H-bonds are listed in Table.4. The molecular

arrangement in the crystal is mainly decided by N-H…O and N-H…Br hydrogen bonds.

The hydrogen bonds N2-H2A…Br (2) [-x+2, y-1/2,-z+1/2] and N2-H2B…O1[x+1, y, z]

interconnect the molecular complex to generate a two dimensional supramolecular network

extending parallel to (0 0 1) plane. Parallel stacking of (0 0 1) two dimensional network along

c-axis is further interlinked through NI-H1B…O2 and N1-H1A…Br1 [x-1/2,-y+1/2,-z]

hydrogen bonds building a three dimensional supramolecular network, which constitutes the

molecular packing of the crystal.

3.3. UV-Vis-NIR spectral analysis

The UV–Vis–NIR spectrum was analysed by Perkin-Elmer Lambda35 spectrometer

with (DBPC) single crystal in the range of 200–1100 nm. The transmission range is important

for any NLO material because it can be of practical use only if it has wide transparency

window. A transparent crystal of 2 mm thickness was used for this measurement. The grown

DBPC crystal has 42% of transparency and UV cut-off wavelength at 235 nm, due

π π* transition in the complex. The transmission spectrum is depicted in Fig.7. The

absence of absorption in the visible range might be due to the filled d 10 orbital of the metal

ion in the complex [25].

7

3.4. Magnetic studies

Magnetic properties were measured using a Vibrating Sample Magnetometer (VSM)

(Lake Shore 7410). Magnetic measurements were carried out on crystalline sample of DBPC

at room temperature. The hysteresis loop of the magnetization versus the magnetic field

strength is shown in Fig.8. The Zn (II), Cd (II) metal complexes possess diamagnetic

properties but some metal coordinated complexes may possess different properties. This

hysteresis looping occurs due to the path dependence of the material response to an external

magnetic field. Crystalline sample of 0.060 g of DBPC with applied field of 15.001×10+3 G

shows that the saturation magnetization (Ms), the remnant magnetization (Mr), retentivity

and coercivity (Hc) are 558.12 ×10-6 emu/g, 368.58×10-9 emu/g, 6.35 ×10-6 emu and

309.81G respectively. The field when the hysteresis loop passes through a zero in

magnetization is called the coercivity of the sample [26–29]. Materials referred to as ‘soft’

have a relatively low coercivity close to zero. This results in a hysteresis loop for soft

materials which would more resemble a single, ‘S’ shaped, curved path passing through the

origin. The coordination environments are changed from tetrahedral to distorted tetrahedral

structure (diamagnetic to soft magnetic nature). The weak interactions of N-H....O, N-H....Br

hydrogen bondings are also responsible for such kind of magnetic properties [30-33].

3.5. Thermal analysis

The TG/DTA of (DBPC) has been recorded by using PerkinElmer Diamond TG/DTA

instrument. A platinum crucible was used for heating the sample and analysis was carried out

in an atmosphere of nitrogen at a heating rate of 10°C/min in the temperature range of

30–450 °C. The initial mass of the material subjected to the analysis was 2.86 mg. The

TG/DTA is shown in the Fig.9. From the TG curve it is understood that the material is stable

up to 218 ºC and on further heating the material suffers weight loss and it follows one stage

weight loss pattern. Only one major weight loss of about 40 % exists in the TGA curve

8

between 220 ºC and 340 ºC. In DTA curve, the sharp endothermic peak at 226 °C is due to

decomposition point of the complex crystals. The sharpness of this endothermic peak shows

good degree of crystallinity and purity of the material and another endothermic peak appears

at 334 ºC. This is due to some complexation in the remaining melt. There is no endothermic

or exothermic peak upto 210 ºC in DTA curve, whereas TGA shows the 40 % weight loss

upto 340 ºC. Hence it is clear that the material is stable upto 218 ºC making it suitable for

possible application in lasers, where the crystal is required to withstand high temperatures.

3.6. Vickers micro hardness measurement

Hardness is a measure of material’s resistance to localized plastic deformation. It

plays a key role in device fabrication. Vickers micro-hardness measurement has been

performed on (DBPC) crystal using MATSUZAWA model MMT-X series micro hardness

tester fitted with diamond indenter. The dwell time was 5 s for all the loads. The indentations

were made using a Vickers pyramidal indenter for loads 1 to 100g. Vickers micro hardness

number (Hv) is evaluated from the relation

Hv = 1.8544P/d2 kg/mm2

where P is the applied load in g and d is the diagonal length of the impression in mm. The

variation in microhardness values with applied load is shown in Fig.10. From Vickers

microhardness studies, it is observed that the hardness value increases up to a load of 100 g.

For load above 100 g cracks developed around the indentation mark, which may be due to the

release of internal stresses.

3.7. Second harmonic studies

Kurtz and Perry [34] second harmonic generation (SHG) test was performed to find

the NLO property of DBPC crystal. A Q-switched Nd: YAG laser was used as light source.

A laser beam of fundamental wavelength 1064 nm, 8 ns pulse width with 10 Hz pulse rate

was made to fall normally on the sample cell. Powdered samples of standard KDP and

9

compound DBPC with the same particle size were considered for powder SHG

measurements. KDP crystal was used as the reference material in the SHG measurement.

The SHG efficiency for DBPC for 2.25 times that of KDP. The SHG measurements on the

crystal of DBPC indicate the potential application of the material for frequency conversion

process.

4. Conclusion

Single crystals of dibromo bis (l-proline) Cd (II) were grown from slow evaporation

solution technique. FT-IR and NMR spectroscopic studies confirm the formation of the

dibromo bis (l-proline) Cd (II) coordinated complex. Single crystal X-ray diffraction analysis

revealed that the compound crystallizes in an orthorhombic system with non-centro

symmetric space group P212121. The grown crystals are transparent in the entire visible

region. The magnetic study reveals that DBPC crystal has soft magnetic property. Thermal

analysis reveals that the material is stable up to 218 ºC. Microhardness study revealed that

the material is stable up to 100 g of load. The second harmonic generation efficiency of

DBPC was 2.25 times that of KDP crystal.

Supplementary information

The crystallographic data of DBPC has been deposited with the Cambridge

Crystallographic Data Centre [CCDC No. 926963]. Copies of the data can be obtained free of

charge at www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge

Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 0

1223 336 033; email: deposit@ccdc.cam.ac.uk].

Acknowledgement

One of the authors (K. Boopathi) is grateful to the SSN Institution for the award of Junior Research Fellowship.

10

Reference

[1] H.S. Nalwa, H.S. Miyata (Eds.), Non-linear Optics of Organic Molecules and

Polymers, CRC Press, Boca Raton, FL, 1997.

[2] P.N. Prasad, D.J. Williams, Introduction to Nonlinear Optical Effects in Organic

Molecules and Polymers, WileyInterscience, New York, 1991.

[3] R.A. Hann, D. Bloor (Eds.), The Royal Society of Chemistry Spec, London, 1989,

pp 176–182.

[4] J. Badan, R. Hierle, A. Perigaud, J. Zuss (Eds.), Non-linear Optical Properties of

Organic Molecules and Polymeric Materials, American Chemical Symposium

Series 233, American Chemical Society, Washington. DC, 1993.

[5] D.S. Chemla, J. Zyss (Eds.), Non-linear Optical Properties of Organic Molecules

and Crystals, Academic Press, Orlando, New York, 1987.

[6] S. Ledoux, J. Zyss, Int. J. Nonlin. Opt. Phys. 3 (1994) 287.

[7] R. Sankar, C.M. Raghavan, R.M. Kumar, R. Jayavel, J. Cryst. Growth 305 (2007)

156.

[8] X.W. Wang, J.Z. Chen, J.H. Liu, Cryst. Growth Des. 7 (2007) 1227.

[9] S.D. Bell, I. Fragalà, Eur. J. Inorg. Chem. (2003) 2606.

[10] N.J. Long, Angew. Chem. Int. Ed. Engl. 34 (1995) 21.

[11] Y. Yukawa, Y. Inomata, T. Takeuchi, M. Shimoi, A. Ouchi, Bull. Chem. Soc.

Japan 55 (1982) 3135.

[12] Y. Yukawa, Y. Inomata, T. Takeuchi, Bull. Chem. Soc. Japan 56 (1983) 2125.

[13] Y. Yukawa, N. Yasukawa, Y. Inomata, T. Takeuchi, Bull. Chem. Soc. Japan 58

(1985) 1592.

[14] K. Li, P.Yang, D. Xue, Acta Materialia, 60 (2012) 35-42

[15]X. Zhao, Z. Bao, C. Sun, and D. Xue, Journal of Crystal Growth 311(2009)

715.

[16] D. Xue and S. Zhang, Journal of Physical Chemistry A 101 (1997) 5550.

11

[17] S. Myung, M. Pink, M.H. Baik, David E. Clemmer, Acta Crystallogr. C 61(2005) o506.

[18] K.Anitha, S. Athimoolam, S. Natarajan, Acta Crystallogr. C62 (2006) o570.

[19] S. Boomadevi, R. Dhanasekaran, J. Cryst. Growth, 261 (2004) 70.

[20] A. Kandasamy, R. Siddeswaran, P. Murugakoothan, P. Suresh Kumar,

R. Mohan, Cryst. Growth Des. 7 (2007) 183.

[22] M. Fleck, P. Held, K. Schwendtner, Bohaty, Z. Krist., 223 (2008)212.

[22] M. Fleck, Z. Kristallogr. 223(2008) 232.

[23] Bruker (2004).APEX2 and SAINT-Plus. Bruker AXS Inc. Madison, Wisconsin, USA.

[24] G.M. Sheldrick, Acta Crystallography, Section A: Foundations of Crystallography

64 (2008) 122.

[25] M.H. Jiang, Q. Fang, Adv. Mater. 11 (1999) 1147.

[26] W.F. Brown, Rev. Mod. Phys. 17 (1945) 15.

[27] A. Aharoni, Rev. Mod. Phys. 34 (1962) 227.

[28] S. Hirosawa, Y. Tsubokawa, J. Magn. Mags. Mater. 84 (1990) 309.

[29] R.C. O’Handley, Modern Magnetic Materials, John Wiley & Sons, New York, 2000

[30] C. J. Lee, H. H Wei, G. H Lee, Y. wang, J.Chin. Chem. Soc. 48 (2001)722.

[31] Y. Yamamoto, T. Suzuki , S. Kaizaki, J. Chem. Soc. Dalton Trans. (2001) 1572.

[32] Y. Yamamoto, T. Suzuki, S. Kaizaki, J. Chem. Soc. Dalton Trans. (2001) 2950.

[33] I. Ratera and J. Veciana Chem. Soc. Rev. 41(2011) 349.

[34] S.K. Kurtz, T.T. Perry, J. Appl. Phys. 39 (1968) 3813.

12

Figure captions

Fig.1. Reaction scheme of DBPC

Fig.2. As grown single crystals of DBPC

Fig.3. FT-IR spectrum of DBPC crystal

Fig.4. (a) 1H NMR spectrum of DBPC (b) 13C NMR spectrum of DBPC

Fig.5. ORTEP view of the molecule with displacement ellipsoids drawn at 40%

Fig.6. Packing arrangements of molecule viewed down the c- axis

Fig.7. UV- visible-NIR transmittance spectrum DBPC crystal

Fig.8. Hysteresis curve of DBPC crystal

Fig.9. TGA and DTA curve of DBPC crystal

Fig.10. Variation of micro hardness number with load

13

HN O

OH

L-proline Cadmium bromide

Cd Br22 H2O

N

C

OO

N

C

O O

CdBr

Br

H

H

H

H

Dibromobis (L-proline) Cd (II)

Fig.1. Reaction scheme of DBPC

Fig.2. As grown single crystals of DBPC

14

4000 3500 3000 2500 2000 1500 1000 500

0

20

40

60

80

100

840

995

937

781

49067

059

4

1050

1082

1161

1190

1259

1331

1415

1538

1633

2564

2434

2564

2732

3028

3465

% t

rans

mit

tanc

e

Wave number (cm-1)

Fig.3. FT-IR spectrum of DBPC crystal

Fi

Fig

ig.4

g.4

4. (a

. (b

a) 1H

b) 13

H N

3C N

NM

NM

15

MR s

MR

d

5

spe

spe

ectru

ectr

c

um

rum

of

m of

b

a

DB

f DB

BPC

BPC

C

C

16

Fig.5. ORTEP view of the molecule with displacement ellipsoids drawn at 40%.

Fig.6. Packing arrangements of molecule viewed down the c- axis

17

Fig.7. UV- visible-NIR transmittance spectrum DBPC crystal

Fig.8. Hysteresis data of DBPC

200 400 600 800 1000

0

10

20

30

40

50

% o

f tra

nsm

itta

nce

Wave length (nm)

-15000 -10000 -5000 0 5000 10000 15000

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

moment(emu)

Field (G)

18

0 100 200 300 400 50050

60

70

80

90

100

110

TGA DTA

Temperature (0C)

Wei

ght

(%)

226.07 oC

334.93 oC

218 oC

-25

-20

-15

-10

-5

0

5

Hea

t fl

ow (

mW

/g)

Fig.9. TGA and DTA curve of DBPC

0 20 40 60 80 100 1205

10

15

20

25

30

35

40

Har

dnes

s nu

mbe

r (k

g/m

m2 )

Load (P)

Fig.10. Variation of micro hardness number with load

19

Table 1: Crystal data and structure refinement for DBPC

Empirical formula C10 H18 Br2 Cd N2 O4

Formula weight 502.48

Temperature 293(2) K

Wavelength 0.71073 A

Crystal system, space group Orthorhombic, P212121

Unit cell dimensions a = 6.7408(3) A alpha = 90 deg.

b = 14.1848(8) A beta = 90 deg.

c = 16.3546(9) A gamma = 90 deg.

Volume 1563.78(14) A^3

Z, Calculated density 4, 2.134 Mg/m^3

Absorption coefficient 6.516 mm^-1

F(000) 968

Crystal size 0.30 x 0.25 x 0.20 mm

Theta range for data collection 2.49 to 26.00 deg.

Limiting indices -5<=h<=8, -17<=k<=17, -20<=l<=17

Reflections collected / unique 8771 / 3065 [R(int) = 0.0248]

Completeness to theta = 26.00 99.90%

Absorption correction Semi-empirical from equivalents

Max. and min. transmission 0.3556 and 0.2453

Refinement method Full-matrix least-squares on F^2

Data / restraints / parameters 3065 / 7 / 193

Goodness-of-fit on F^2 0.922

Final R indices [I>2sigma(I)] R1 = 0.0210, wR2 = 0.0434

R indices (all data) R1 = 0.0266, wR2 = 0.0451

Absolute structure parameter 0.003(7)

Extinction coefficient 0.0044(2)

Largest diff. peak and hole 0.287 and -0.298 e.A^-3

Table.2. Bond lengths [A] for DBPC

20

Band length [A]

C(1)-O(2) 1.224(4)

C(1)-O(1) 1.269(4)

C(1)-C(2) 1.508(4)

C(2)-N(1) 1.510(5)

C(2)-C(3) 1.523(5)

C(2)-H(2) 0.9800

C(3)-C(4) 1.486(8)

C(3)-C(4') 1.512(7)

C(3)-H(3A) 0.9700

C(3)-H(3B) 0.9700

C(3)-H(3C) 0.9700

C(3)-H(3D) 0.9700

C(4)-C(5) 1.461(9)

C(4)-H(4A) 0.9700

C(4)-H(4B) 0.9700

C(4)-H(5D) 1.5877

C(4')-C(5) 1.426(7)

C(4')-H(4C) 0.9700

C(4')-H(4D) 0.9700

C(5)-N(1) 1.475(5)

C(5)-H(5A) 0.9700

C(5)-H(5B) 0.9700

C(5)-H(5C) 0.9700

C(5)-H(5D) 0.9700

C(6)-O(4) 1.214(4)

C(6)-O(3) 1.256(4)

C(6)-C(7) 1.520(5)

C(7)-N(2) 1.499(4)

C(7)-C(8) 1.511(5)

C(7)-H(7) 0.9800

C(8)-C(9) 1.489(6)

C(8)- H(8A) 0.9700

C(8)-H(8B) 0.9700

C(9)-C(10) 1.499(6)

C(9)-H(9A) 0.9700

C(9)-H(9B) 0.9700

C(10)-N(2) 1.488(5)

C(10)-H(10A) 0.9700

C(10)-H(10B) 0.9700

N(1)-H(1B) 0.901(10)

N(1)-H(1A) 0.897(10)

N(2)-H(2A) 0.906(10)

N(2)-H(2B) 0.901(10)

O(1)-Cd(1) 2.214(2)

O(3)-Cd(1) 2.188(3)

Cd(1)-Br(1) 2.5345(5)

Cd(1)-Br(2) 2.6051(4)

21

Table.3. Bond angles [deg] for DBPC

Band angle [deg]

O(2)-C(1)-O(1) 125.5(3)

O(2)-C(1)-C(2) 120.3(3)

O(1)-C(1)-C(2) 114.2(3)

C(1)-C(2)-N(1) 108.8(3)

C(1)-C(2)-C(3) 112.5(3)

N(1)-C(2)-C(3) 103.9(3)

C(1)-C(2)-H(2) 110.5

N(1)-C(2)-H(2) 110.5

C(3)-C(2)-H(2) 110.5

C(4)-C(3)-C(4') 33.3(4)

C(4)-C(3)-C(2) 106.2(4)

C(4')-C(3)-C(2) 105.3(4)

C(4)-C(3)-H(3A) 110.5

C(4')-C(3)-H(3A) 136.3

C(2)-C(3)-H(3A) 110.5

C(4)-C(3)-H(3B) 110.5

C(4')-C(3)-H(3B) 80.4

C(2)-C(3)-H(3B) 110.5

H(3A)-C(3)-H(3B) 108.7

C(4)-C(3)-H(3C) 79.6

C(4')-C(3)-H(3C) 110.4

C(2)-C(3)-H(3C) 110.9

H(3A)-C(3)-H(3C) 32.7

H(3B)-C(3)-H(3C) 132.1

C(4)-C(3)-H(3D) 135.4

C(4')-C(3)-H(3D) 110.8

C(2)-C(3)-H(3D) 110.6

H(3A)-C(3)-H(3D) 79.2

H(3B)-C(3)-H(3D) 32.2

N(1)-C(5)-H(5C) 110.4

H(5A)-C(5)-H(5C) 33.6

H(3C)-C(3)-H(3D) 108.8

C(5)-C(4)-C(3) 106.2(5)

C(5)-C(4)-H(4A) 110.5

C(3)-C(4)-H(4A) 110.5

C(5)-C(4)-H(4B) 110.5

C(3)-C(4)-H(4B) 110.5

H(4A)-C(4)-H(4B) 108.7

C(5)-C(4)-H(5D) 36.8

C(3)-C(4)-H(5D) 129.7

H(4A)-C(4)-H(5D) 75.0

H(4B)-C(4)-H(5D) 114.6

C(5)-C(4')-C(3) 106.6(4)

C(5)-C(4')-H(4C) 110.4

C(3)-C(4')-H(4C) 110.4

C(5)-C(4')-H(4D) 110.4

C(3)-C(4')-H(4D) 110.4

H(4C)-C(4')-H(4D) 108.6

C(4')-C(5)-C(4) 34.6(4)

C(4')-C(5)-N(1) 106.1(4)

C(4)-C(5)-N(1) 106.3(4)

C(4')-C(5)-H(5A) 78.8

C(4)-C(5)-H(5A) 110.5

N(1)-C(5)-H(5A) 110.5

C(4')-C(5)-H(5B) 136.4

C(4)-C(5)-H(5B) 110.5

N(1)-C(5)-H(5B) 110.5

H(5A)-C(5)-H(5B) 108.7

C(4')-C(5)-H(5C) 110.5

C(4)-C(5)-H(5C) 136.2

C(10)-C(9)-H(9B) 110.9

H(9A)-C(9)-H(9B) 108.9

22

H(5B)-C(5)-H(5C) 78.0

C(4')-C(5)-H(5D) 110.5

C(4)-C(5)-H(5D) 78.7

N(1)-C(5)-H(5D) 110.7

H(5A)-C(5)-H(5D) 132.8

H(5B)-C(5)-H(5D) 33.7

H(5C)-C(5)-H(5D) 108.7

O(4)-C(6)-O(3) 126.1(3)

O(4)-C(6)-C(7) 119.9(3)

O(3)-C(6)-C(7) 113.9(3)

N(2)-C(7)-C(8) 104.8(3)

N(2)-C(7)-C(6) 111.1(3)

C(8)-C(7)-C(6) 117.7(3)

N(2)-C(7)-H(7) 107.6

C(8)-C(7)-H(7) 107.6

C(6)-C(7)-H(7) 107.6

C(9)-C(8)-C(7) 103.5(3)

C(9)-C(8)-H(8A) 111.1

C(7)-C(8)-H(8A) 111.1

C(9)-C(8)-H(8B) 111.1

C(7)-C(8)-H(8B) 111.1

H(8A)-C(8)-H(8B) 109.0

C(8)-C(9)-C(10) 104.4(3)

C(8)-C(9)-H(9A) 110.9

C(10)-C(9)-H(9A) 110.9

C(8)-C(9)-H(9B) 110.9

N(2)-C(10)-C(9) 104.6(3)

N(2)-C(10)-H(10A) 110.8

C(9)-C(10)-H(10A) 110.8

N(2)-C(10)-H(10B) 110.8

C(9)-C(10)-H(10B) 110.8

H(10A)-C(10)-H(10B) 108.9

C(5)-N(1)-C(2) 108.9(3)

C(5)-N(1)-H(1B) 118(3)

C(2)-N(1)-H(1B) 101(3)

C(5)-N(1)-H(1A) 113(3)

C(2)-N(1)-H(1A) 104(3)

H(1B)-N(1)-H(1A) 111(4)

C(10)-N(2)-C(7) 108.0(3)

C(10)-N(2)-H(2A) 110(4)

C(7)-N(2)-H(2A) 103(4)

C(10)-N(2)-H(2B) 107(3)

C(7)-N(2)-H(2B) 115(3)

H(2A)-N(2)-H(2B) 113(4)

C(1)-O(1)-Cd(1) 115.3(2)

C(6)-O(3)-Cd(1) 105.9(2)

O(3)-Cd(1)-O(1) 93.25(10)

O(3)-Cd(1)-Br(1) 128.08(7)

O(1)-Cd(1)-Br(1) 125.05(7)

O(3)-Cd(1)-Br(2) 99.26(7)

O(1)-Cd(1)-Br(2) 97.19(6)

Br(1)-Cd(1)-Br(2) 107.758(15)

23

Table.4. Hydrogen bonds for DBPC [A and deg.].

Symmetry transformations used to generate equivalent atoms:

a -x+2, y-1/2,-z+1/2 b x+1, y, z c x-1/2,-y+1/2,-z

D-H...A d(D-H) d(H...A) d(D...A) <(DHA)

N(2)-H(2A)...Br(2)a 0.906(10) 2.362(15) 3.257(3) 170(5)

N(2)-H(2B)...O(1)b 0.901(10) 2.01(2) 2.843(4) 152(4)

N(1)-H(1B)...O(2) 0.901(10) 2.07(4) 2.661(4) 122(4)

N(1)-H(1A)...Br(1)c 0.897(10) 2.64(3) 3.448(3) 150(4)

24

Graphical Abstract

25

Highlights

• Good quality single crystals of dibromo bis (l-proline) Cd (II) in an orthorhombic

system with P212121 were grown.

• Metal–ligand coordination, structural properties and hydrogen bonds are discussed.

• At room temperature DBPC possess soft magnetic properties

• DBPC crystal is thermally stable up to 218 ˚C

• SHG efficiency of the DBPC is 2.25 times that of KDP crystal