Molecular structural identification and position of Cu(II) ion in Diaqua(2,2′-bipyridine)malonatozinc(II): Spectroscopic studies

Molecular structural identification and position of Cu(II) ion in Diaqua(2,2′-bipyridine)malonatozinc(II): Spectroscopic studies

Journal of Molecular Structure 977 (2010) 130–136 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.els...

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Journal of Molecular Structure 977 (2010) 130–136

Contents lists available at ScienceDirect

Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc

Molecular structural identification and position of Cu(II) ion in Diaqua(2,20 -bipyridine)malonatozinc(II): Spectroscopic studies Krishnan Parthipan, P. Sambasiva Rao * Department of Chemistry, Pondicherry University, Puducherry 605 014, India

a r t i c l e

i n f o

Article history: Received 12 April 2010 Received in revised form 13 May 2010 Accepted 14 May 2010 Available online 24 May 2010 Keywords: EPR Single crystal Interstitial Spin Hamiltonian Admixture coefficient

a b s t r a c t Electron paramagnetic resonance, optical, FTIR and powder XRD studies have been carried out on Cu(II) doped diaqua(2,20 -bipyridine)malonatozinc(II) complex to get information about the effect of the dopant. Angular variation of copper hyperfine lines in EPR study shows the presence of a single site with g and A values as: gxx = 2.121, gyy = 2.066, gzz = 2.424 and Axx = 2.09 mT, Ayy = 3.62 mT, Azz = 14.18 mT. The direction cosines of principle g and A values suggest that the impurity is present interstitially in the lattice and the location has been identified. Admixture coefficients and molecular orbital parameters have also been evaluated. Optical, FTIR and powder XRD techniques have been used to reconfirm the structure of the complex. Ó 2010 Elsevier B.V. All rights reserved.

1. Introduction Structure and spectral investigation of transition metal complexes containing malonic acid are quite interesting because the malonate dianion acts as a good bidentate versatile ligand and it exhibits different configurations like syn–syn and anti–anti through one or both carboxylate groups. Usually coordination complexes containing bipyridine with malonato-bridged ligand have wide variety of applications as materials in catalysts, molecular electronics, biologically active compounds, molecular-based magnetic materials and polymorphs [1,2]. In addition, the carboxylate group provides an efficient pathway for coupling magnetic centers either ferromagnetic or antiferromagnetic [3–7]. In these kinds of systems, the coupling constant is influenced by structural factors such as the conformation of bridge or the geometry of the metal environment [8]. Copper complexes show broad EPR resonance due to the presence of dipole–dipole interaction and it also prevents such kind of interaction in dilute forms. EPR study of copper complexes have gained more importance in a wide range of symmetrical environments, viz. tetrahedral [9], octahedral [10,11] and square planar [12], trigonal bipyramidal [13,14] and square pyramidal [15–17]. The present work deals with the EPR of Cu(II) doped in diaqua(2,20 -bipyridine)malonatozinc(II) (abbreviated as DBMZ). It is more interesting because dopant Cu(II) has been used as an EPR probe to studying the possible geometries and corresponding ground state energy level of copper(II) com* Corresponding author. Tel.: +91 413 2654412; fax: +91 413 2655987. E-mail address: [email protected] (P. Sambasiva Rao). 0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2010.05.023

plexes. Most of the paramagnetic impurities have entered into the zinc malonato complexes interstitially, because the breaking of malonate dianions is difficult. In the present case, paramagnetic impurity Cu(II) has been entered interstitially, which is favorable due to bipyridine nitrogen and carboxylate oxygen chelating part. 2. Experimental Single crystals of copper doped DBMZ used in this study were all grown, which is accomplished with a procedure as follows [18]. An alcoholic solution of 2,20 -bipyridine and aqueous solution (10 ml) of ZnCl24H2O (0.198 g, 1 mmol) were refluxed for 30 min. The large amount of precipitate was produced. At this stage, 0.1% by weight of copper chloride was added as dopant. An aqueous solution (10 ml) of malonic acid (0.116 g, 1 mmol) neutralized with an aqueous solution of NaOH was added gradually to the above reaction mixture with continuous stirring and refluxing until the precipitate had dissolved. After half an hour, the reaction mixture was cooled to the room temperature for crystal growth. After 2 weeks, good and well shaped crystals were separated out from the solution. 2.1. EPR studies The EPR spectra were recorded at room temperature on a JEOL JES-TE100 ESR spectrometer operating at X-band frequencies, having a 100 kHz field modulation to obtain the first derivative EPR spectrum. DPPH was used as the standard for magnetic

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field correction for g-factor calculations. Angular variation was made at room temperature by rotating the crystal along the three mutually orthogonal axes a, b, c in 10° interval. Isofrequency plots of each plane were simulated using program EPRNMR [19]. The EPR spectrum of powder sample was simulated using Simfonia program developed and supported by Bruker Biospin.

2.2. Optical absorption Optical spectrum of copper doped DBMZ was recorded at room temperature using a Varian Cary 5000 Ultraviolet (UV–Visible) near infrared spectrophotometer in the region of 200–1200 nm.

2.3. FTIR and powder XRD studies FTIR spectrum of copper doped DBMZ was recorded at room temperature. In the present study, the FTIR spectra were recorded on a Shimadzu FTIR-8300/8700 spectrometer in the region of 4000–400 cm1. The measurements were made using almost transparent KBr pellets containing fine powder sample at room temperature. In the crystalline material, the powder X-ray diffraction (XRD) was used to identify and characterize the powder sample possessing a long and shot range order respectively. In the present investigation, powder XRD were carried out for doped and undoped materials on a PANalytical Xpert Pro diffractometer with Cu Ka radiation of wavelength 0.15406 nm and 2h values of 5–75°.

3. Crystal structure DBMZ ([Zn(C3H2O4)(C10H8N2)(H2O)2]) is isostructural with [Mn(C3H2O4)(C10H8N2)(H2O)2] and belongs to monoclinic crystal class with space group P21/c, having unit cell parameters a = 0.7834, b = 0.9408, c = 2.0532 nm and b = 97.75° and Z = 4. The Zn(II) atom demonstrates a distorted octahedral geometry being coordinated by two N atoms from 2,20 -bipyridine ligand, two O atoms from the carboxylate groups of the chelating malonate dianion and two O atoms of two cis water molecules [18]. The molecular packing diagram of DBMZ is shown in Fig. 1.

4. Results and discussion 4.1. Optical absorption studies of Cu(II) doped DBMZ Copper ion has 3d9 configuration with 2D ground state. The broad adsorption band observed is due to the transition between the levels 2Eg and 2T2g The d9 electronic configuration of this ion gives three electrons in the two degenerate Eg orbitals leading to a doubly-degenerate electronic ground state which causes distortion in the octahedral symmetry. In tetragonal distorted octahedral symmetry (C4v), 2Eg splits into 2B1g (corresponding to dx2y2) and 2 2 A1g (corresponding to dz ) while 2T2g splits into 2B2g (corresponding 2 to dxy) and Eg (corresponding to dxz, dyz). The optical absorption spectra recorded at room temperature is shown in Fig. 2. It shows four characteristic bands at 304, 422, 826 and 1010 nm. The band at 304 nm is due to charge transfer band and remaining three are d–d transition bands. The distortion is attributed only to tetragonal and not to any other lower symmetry. Accordingly, the bands are attributed to the transitions 2B1g ? 2Eg, 2B1g ? 2B2g, 2B1g ? 2A1g respectively. The crystal field stabilization energy parameters Dq, Dt, Ds are calculated with help of the below equations [19]. 2

B1g ! 2 Eg ! E1 ¼ 10Dq þ 3Ds  5Dt

2

B1g ! 2 B2g ! E2 ¼ 10Dq

2

B1g ! 2 A1g ! E3 ¼ 4Ds þ 5Dt

Here Dq is the octahedral crystal field parameter and Ds and Dt are the tetragonal crystal field parameters respectively, the parameters evaluated from the above expressions are

Dq ¼ 1212;

Ds ¼ 1674 and Dt ¼ 641 cm1

The crystal field parameters confirm a tetragonal distortion for copper ion in the DBMZ lattice. 4.2. FTIR and powder XRD studies of Cu(II) doped DBMZ The FTIR spectrum of Cu(II)/DMBZ is recorded at room temperature. The band observed at 1655 cm1 is assigned to the carboxylate (COO) symmetrical stretching and the bands appeared around 3436 and 3105 are assigned to O–H bending corresponding to water ligand. Three bands observed at 975, 788 and 732 cm1 corresponds to bending modes of O–C–O bond. The band observed at 1445 cm1 has been assigned to [email protected] stretching. The bands observed at 1576 and 976 cm1 are assigned to bipyridyl stretching. Copper oxygen and copper nitrogen vibrations are not seen due to very low concentration of the impurity. However, this spectrum is

0.8

32894 cm -1

Absorbance (a.u.)

0.6

0.4 23696 cm -1 12106 cm -1

0.2

9901 cm -1

0.0

-0.2 200

400

600

800

1000

1200

wave length (nm)

Fig. 1. Molecular packing diagram for DBMZ [18].

Fig. 2. Powder optical absorption spectrum of Cu(II) doped DBMZ at room temperature.

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helpful to confirm that no structural changes have occurred after doping DBMZ with Cu(II) ions. The powder XRD pattern of Cu(II) doped DBMZ and pure DBMZ were recorded at room temperature. Crystal lattice parameters a, b, c for both copper doped DBMZ and pure DBMZ have been calculated from powder XRD. These values agree with reported values for DBMZ and it confirms that the formation of lattice DBMZ. Low concentration of copper impurity does not alter structure.

planes. It indicates a single magnetically distinct copper ion present in the lattice even though the unit cell contains four molecules (Z = 4). Two more EPR spectra in ac and bc plane are given in Figs. 3b and 3c respectively at the indicated orientations. Figs. 4a–4c show the angular variation of hyperfine lines in the three planes bc, ab and ac respectively. In these figures, solid circle represents experimental points whereas the continuous straight line represents simulated points. A good agreement has been found.

4.3. EPR studies 4.4. Calculation of spin Hamiltonian parameters Single crystal of Cu(II)/DBMZ, in the form of good shape crystal was selected and inserted into the EPR cavity by mounting it along with the crystallographic axis a for room temperature for measurements. Cu(II) ion is a d9 system with S = 1/2 and I = 3/2 (for both 63 Cu and 65Cu naturally abundant isotopes). Therefore, one would expect four hyperfine lines in all the three planes ab, bc and ac. Here, b is the crystallographic axis b, axis a is orthogonal to axis b in ab plane and c is mutually perpendicular to both axes b and a. One such a spectrum in the ab plane for B parallel to axis a is shown in Fig 3a. Only a maximum of four line patterns have been observed during the crystal rotations for all the three orthogonal

As the copper ion has 3d9 electronic configuration, it contains a single unpaired electron (S = 1/2) interacting with nucleus (I = 3/2). The spin Hamiltonian used for calculating spin Hamiltonian parameters for Cu(II) ion has the form

Hs ¼ g xx bBx Sx þ g yy bBy Sy þ g zz bBz Sz þ Axx Sx Ix þ Ayy Sy Iy þ Azz Sz Iz It includes only electron Zeeman and hyperfine interactions. The quadrupole and nuclear Zeeman interactions have been ignored. The spin orbit interaction is intrinsic in g and A tensors constructed and diagonalized to find the principle values. By making

Fig. 3a. Single crystal EPR spectrum of Cu(II)/DBMZ, when applied magnetic field (B) is parallel to axis a. Frequency = 9.07554 GHz.

Fig. 3b. Single crystal EPR spectrum of Cu(II)/DBMZ, when B is parallel to the axis c. Frequency = 9.06856 GHz.

Fig. 3c. Single crystal EPR spectrum of Cu(II)/DBMZ recorded, when B is parallel to axis b. Frequency = 9.06849 GHz.

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3200

Table 1 Spin Hamiltonian parameters obtained from the single crystal rotations for Cu(II) in DBMZ using program EPR-NMR [20]. Uncertainties in g is ±0.005 and in A is ± 0.05 mT.

Magnetic field (mT)

3100 3000

Principle values

Direction cosines a

b

c

0.094 0.103 2.214

2.121 2.066 2.424

0.7554 0.3489 0.5545

0.6548 0.4307 0.6209

0.0221 0.8322 0.5539

3.08 4.30 6.90

3.62 2.09 14.18

0.3763 0.7515 0.5417

0.7969 0.0356 0.6030

0.4724 0.6586 0.5855

2900 g Matrix 2.182 0.132 2.214

2800 2700 2600

A matrix (mT) 6.50 3.91 6.49

2500 2400

0

20

40

60

80

100

120

140

160

180

θ (degree) Fig. 4a. Angular variation plot of Cu(II) doped DBMZ in the ac plane. Frequency = 9.07554 GHz.

Table 2 Spin Hamiltonian parameters for Cu(II) in DBMZ and few related host lattices. Lattices

3200

Magnetic field (mT)

3100 DBMZ Powder DBMZ DABMZa DAMZb ZPPHe CoAPHc AMMZd

3000 2900 2800 2700

a

2600

b

2500

d

c

e

2400

0

20

40

60

80

100

120

140

160

3200

Magnetic field (mT)

3100 3000 2900 2800 2700 2600 2500 20

40

60

80

100

gzz

gxx

gyy

Azz

Axx

Ayy

2.424 2.391 2.455 2.442 2.372 2.404 2.379

2.121 2.080 2.121 2.087 2.188 2.151 2.100

2.066 2.080 2.105 2.077 2.032 2.063 2.076

14.18 12.52 16.09 14.74 8.00 11.58 13.47

3.62 – 1.25 2.88 6.50 3.49 3.22

2.1 – 0.73 1.83 5.0 2.09 2.47

Reference

Present case [26] [27] [30] [28] [32]

DABMZ, diaquabis[malonato(1-)-k2O,O0 ] zinc(II). DAMZ, diaqua malonatozinc (II). CoAPH, cobalt ammonium phosphate hexahydrate. AMMZ, aquamethylmelonatozinc(II). ZPPH, zinc potassium phosphate hexahydrate.

2

Fig. 4b. Angular variation plot of Cu(II) doped DBMZ in the ab plane. Frequency = 9.06856 GHz.

0

Hyper fine constant A (mT)

180

θ (degree)

2400

Spectroscopic splitting

120

140

160

180

the ground state is predominantly dz and if it is less than unity, it means that the unpaired electron is present in dx2y2 state. The calculated value of R in the present case is 0.154, which is less than unity, suggests that the ground state of Cu(II) in DBMZ lattice is dx2y2. The direction cosines of principal g and A values are very close to each other suggesting that the tensors are coincident, which further confirmed by having the maxima and minima at the same angle in the isofrequency plots of all the three planes. Generally the direction cosines of principal g/A values are compared with the direction cosines of metal–ligand bond directions obtained from crystallographic data (Zn–O, and Zn–N) to get information about the location of the dopant. The direction cosines of the Zn–O and Zn–N direction have been calculated from the crystal data of the host lattice [18] and are given in Table 3. The crystal structure of DBMZ is shown in Fig. 1. When these direction cosines are compared with those of g and A, none of them matched. This indicates that the paramagnetic Cu(II) impurity might have entered the lattice interstitially and not substitutionally. The orientations of the copper ion have also been discussed.

θ (degree) Fig. 4c. Angular variation plot of Cu(II) doped DBMZ in the bc plane. Frequency = 9.06849 GHz.

use of program EPR-NMR [20], the spin Hamiltonian parameters g and A have been evaluated using the isofrequency plots and the values are given in Table 1 along with respective direction cosines. The spin Hamiltonian parameters for few related host lattices are listed in Table 2 along with Cu(II) doped DBMZ. The spin Hamiltonian parameters obtained in the present case are characteristic of Cu(II) ion in orthorhombic symmetry. If the R factor given by R = (gx  gy)/(gz  gx) (where gz > gx > gy) is greater than unity, then

4.5. Orientations of the Cu(II) ions in the lattice As the impurity has entered interstitially, a number of locations are assumed from the XRD data of the host lattice. Using the fractional coordinates and unit cell dimensions [18], the Cartesian coordinates for the zinc atoms and surrounding oxygen and nitrogen atoms in the unit cell can be calculated. The interstitial location for the Cu(II) is calculated and given in Fig. 6. It can be suggested that Cu(II) ion occupies the interstitial position surrounded either by bipyridine nitrogens or carboxylic oxygens. In this case, Cu(II) is surrounded by two nitrogens and one oxygen N(1), N(2), O(3) which are connected to Zn(1). The other two nitro-

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Table 3 Direction cosines of Zn–O, Zn–N bands in DBMZ lattice for site-I and site-II. Crystal data

Direction cosines of metal–nitrogen and metal oxygen bond

Hamiltonian parameters have been calculated from powder spectrum and the values are given below;

g k ¼ 2:391;

g ? ¼ 2:080: Ak ¼ 12:52 mT;

a

b

c

Site-I Zn(1)–N(1) Zn(1)–N(2) Zn(1)–O(1) Zn(1)–O(3) Zn(1)–O(5) Zn(1)–O(6)

0.1067 0.1346 0.0526 0.9918 0.9910 0.0160

0.7982 0.2619 0.5248 0.0735 0.1142 0.9561

0.5597 0.9556 0.8498 0.1038 0.0688 0.2919

The g and A values for Cu(II)doped DBMZ powder are close to those obtained for single crystal (Table 1). The parallel g value is greater than perpendicular value indicating that the ground state is dx2y2. The powder spectrum is also simulated and is given along with experimental one in Fig. 5, where the agreement is good.

Site-II Zn(2)–N(1)0 Zn(2)–N(2)0 Zn(2)–O(1) Zn(2)–O(3) Zn(2)–O(5) Zn(2)–O(6)

0.1072 0.1339 0.0530 0.9918 0.9910 0.0152

0.8220 0.2618 0.5244 0.0741 0.1139 0.9563

0.5597 0.9556 0.8498 0.1038 0.0689 0.2914

4.7. Calculation of admixture and molecular orbital parameters

Interstitial location Cu–N(1) 0.6773 Cu–N(2) 0.6690 Cu–O(3) 0.0235 Cu–N(1)0 0.6550 Cu–N(2)0 0.6690 Cu–O(3)0 0.0238

0.3274 0.5406 0.1654 0.3169 0.5400 0.1652

0.6580 0.5097 0.9749 0.6370 0.5099 0.9749

The oxygen atoms labeled (1) and (3) represent for malonato oxygen and (5) and (6) represent to water oxygen. N(1) and N(2) represent to 2,2-bipyridine ligand.

gens namely N(1)0 , N(2)0 and one oxygen O(3)0 are connected to another Zn(2) atom. One of the direction cosines of the new location of Cu(II) ion, Cu(II)–N(2), matches with one of the direction cosines of the g and A matrix. The direction cosines of the four (impurity) Cu–N and two Cu–O atoms are shown in Table 2. Here the impurity location along with the six atoms namely four nitrogens from 2,20 bipyridine and two oxygens from malonate ligand has been roughly assumed as a distorted octahedral structure. 4.6. Polycrystalline EPR spectrum The single crystal data is generally crosschecked using the polycrystalline sample. The EPR spectrum of the polycrystalline sample is recorded at room temperature and is shown in Fig. 5. The spin

and A? was not resolved:

The spin Hamiltonian parameters indicate dx2y2 ground state of the Cu(II) ions. The non-axial symmetry of the g and A tensor suggest a rhombic crystal field symmetry. The wave function for the ground state Kramers’ is

W ¼ a/1 a þ b/3 a þ ic/2 a  id/4 b  e/5 b W ¼ iða/1 b þ b/3  ic/2  id/4 þ e/5 aÞ 2

where /1 = dz (A), /2 = dxy (B1), /3 = dx2y2 /4 = dyz (B3), /5 = dxz (B2) 2 [21]. Equation represents that if a = 1, the system has the dz ground state and lowest A|| value and if b = 1, the system is in dx2y2 ground state and has the maximum hyperfine value. a, b, c, d and e are the coefficients of /1, /2, /3, /4 and /5 respectively. These coefficients do not reflect the covalency of the metal ligand bonds but rather restrict themselves to give an indication of the mixing among the dorbitals brought about by metal spin–orbital coupling. Here, the cross terms involving ligand spin–orbit coupling are neglected. The expression for the g-vales (in terms of admixture coefficients) are given as [21]. 2

g z ¼ 2  4d  4e2 þ 8bc þ 4de pffiffiffi g x ¼ 2  4c2  4e2 þ 4 3ad  4ce þ 4bd pffiffiffi 2 g y ¼ 2  4c2  4d þ 4 3ae  4be þ 4cd Using the normalization condition and assuming e = d, values of a, b, c and d are obtained by iterative procedure. The coefficients, which gave the best fit to the observed g values are listed in Table 4

Fig. 5. EPR spectrum of powder sample of Cu(II)/DBMZ at room temperature (top) whereas the bottom one corresponds to simulated spectrum using simfonia program. Frequency = 9.07971 GHz.

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135

Fig. 6. An interstitial location giving a distorted octahedral structure to copper ion in the DBMZ lattice (see text for details).

Table 4 d-Orbital coefficients of the ground state wave function for Cu(II) in DBMZ and few related Cu(II) systems in low symmetry environments.

a b c d

Compound

a

b

c

d

e

Reference

DBMZ DABMZa SCCd DAMZb CoAPHc

0.144 0.144 0.144 0.281 0.250

0.988 0.988 0.988 0.957 0.966

0.052 0.058 0.041 0.057 0.052

0.019 0.019 0.019 0.032 0.021

0.019 0.019 0.019 0.032 0.021

Present [26] [29] [27] [28]

DABMZ, diaquabis[malonato(1-)-k2O,O0 ] zinc(II). DAMZ, diaqua malonatozinc (II). CoAPH, cobalt ammonium phosphate hexahydrate. SCC, sacrosine cadmium chloride.

The values of P and k obtained for our present system 312  104 cm1 and 0.35, respectively. The ratio of P values obtained for complex to that of the free ion value is around 87%, indicating the localization of d-electron. The percentage of unpaired spin density on copper ion is 13% and the remaining density is being distributed onto the ligands. The molecular orbital coefficient a2 which gives a measure of covalent nature of r-bonding is given as [25].

a2 ¼ Ak =0:036 þ ðg k  2:0023Þ þ 3=7ðg ?  2:0023Þ þ 0:04 a0 can be evaluated from the normalization condition on the ground state orbital as

and compared with those reported for a few other systems. A comparison of these results reveals that there is considerable admixture of d-orbitals in the present compounds. The dipolar term P and Fermi contact parameter j are evaluated [22,23] from the following expressions.

Ak ¼ P½ð4a2 =7Þ  k þ ðg k  g e Þ þ 3=7ðg ?  g e Þ

a0 ¼ ð1  a2 Þ1=2 þ aS; where S is the overlap integral between the dx2y2 orbital and normalized ligand orbital. The value of S is given as 0.076 for copper complex. This complex found to be partially covalent nature. For Cu/DBMZ the bonding parameter

A? ¼ P½2a2 =7Þ  k þ 11=14ðg ?  g e Þ

a2 ¼ 0:78; a ¼ 0:88; a0 ¼ 0:5276

Here P = 2cCubbn hr3i, cCu is the gyromagnetic ratio of copper, b is the Bohr magneton and bn is the nuclear magneton, and j is the dimension less hyperfine interaction constant. The average of Ax and Ay is taken as A\. These parameters are calculated for Cu(II)/ DBMZ and tabulated in Table 5 with other related systems for comparison. According to Kivelson and Neiman, k = a2k0, where k0 is the free ion parameter which estimated by Abragam and Pryce to be 0.36 [24]. Using the above expression, the values of P and k can be calculated. The P value for free ion is 360  104 cm1.

The value of a2 is unity if the bond between metal and the ligands is ionic and 0.5, if it is covalent. The present value 0.780 indicates partially covalent nature for the metal ligand bond. Hence, 2 admixture of dx2y2 and dz orbital and covalency contribute to the low magnitude of the Cu(II) hyperfine constant [26–32].

Table 5 Molecular orbital coefficient for some Cu(II) systems.

a b C d

Compound

a2

j

P (104 cm1)

Reference

DBMZ DAMZb ZPPHd Zn(Im)6Cl24H2O DABMZa AMMZc

0.780 0.790 0.678 0.884 0.869 0.780

0.350 0.284 0.281 0.721 0.476 0.350

312 240 165 185 243 303

Present [27] [30] [31] [26] [32]

DABMZ, diaquabis[malonato(1-)-k2O,O0 ] zinc(II). DAMZ, diaqua malonatozinc (II). AMMZ, aquamethylmelonatozinc(II). ZPPH, zinc potassium phosphate hexahydrate.

5. Conclusion EPR studies of Cu(II) doped DBMZ have been evaluated at room temperature. Single crystal rotations in the three planes indicate that only one site noticed for copper impurity present in DBMZ lattice. The spin Hamiltonian parameters have been calculated and direction cosines values confirm that the impurity has entered the lattice in an interstitial position. The isofrequency plots and the powder EPR spectrum have been simulated, which confirm the evaluated spin Hamiltonian parameters. The location of the interstitial position has been identified. Fermi contact term and dipolar interaction parameter have also been evaluated. From the optical data, the crystal field parameter (Dq) and the tetragonal parameters (Ds and Dt) have been calculated. Zn–O, –COO–, –OH bonds are confirmed by FTIR. Powder XRD confirms the structure of the lattice DBMZ.

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