Construction of mononuclear macrocyclic and dinuclear acyclic Schiff base complexes via cadmium(II)–ion template: Synthesis, characterisation, and crystal structures

Accepted Manuscript Construction of Mononuclear Macrocyclic and Dinuclear Acyclic Schiff Base Complexes via Cadmium(II)–Ion Template: Synthesis, Characterisation, and Crystal Structures Leila Noohinejad, Seyed Abolfazl Hosseini–Yazdi PII: DOI: Reference:

S0020-1693(17)31625-0 https://doi.org/10.1016/j.ica.2017.11.064 ICA 18034

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Inorganica Chimica Acta

Please cite this article as: L. Noohinejad, S.A. Hosseini–Yazdi, Construction of Mononuclear Macrocyclic and Dinuclear Acyclic Schiff Base Complexes via Cadmium(II)–Ion Template: Synthesis, Characterisation, and Crystal Structures, Inorganica Chimica Acta (2017), doi: https://doi.org/10.1016/j.ica.2017.11.064

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Construction of Mononuclear Macrocyclic and Dinuclear Acyclic Schiff Base Complexes via Cadmium(II)–Ion Template: Synthesis, Characterisation, and Crystal Structures Leila Noohinejada , Seyed Abolfazl Hosseini–Yazdia, a

Department of Inorganic Chemistry, Faculty of Chemistry, University of Tabriz, 51666-14766 Tabriz, Iran

Abstract Using a metal template approach a series of mono and dinuclear cadmium(II) were synthesized by Schiff base condensation of a pendant armed dialdehyde, i.e. 2-[3-(2-formylphenoxy)-2-hydroxypropoxy] benzaldehyde (PL) with selection of different diamines, diethylenetriamine, dipropylenetriamine, 1,2diaminopropane and 1,2-diaminoethane. Depending on the nature of the diaminoalkane spacers and metal ion, 1:1 (metal:ligand) macrocyclic (L1OH and L2OH) or 2:1 (metal:ligand) acylic (L3O− and L4O− ) complexes of cadmium(II) were obtained. With the longer spacers diethylenetriamine and dipropylenetriamine ring closure around the cadmium ion was observed and [1+1] macrocyclic Schiff base ligands (L1OH and L2OH) were formed. With the shorter spacers 1,2-diaminopropane and 1,2-diaminoethane ring closure was not observed. Interestingly, the dialdehyde PL reacted with two molecules of diamine, forming intermediate product acyclic Schiff base [1+2] ligands (L3O− and L4O− ) that are coordinated to two cadmium ions Email address: [email protected] (Seyed Abolfazl Hosseini–Yazdi) Preprint submitted to Inorganic Chimica Acta

December 13, 2017

to form dinuclear complexes. Crystal structures indicated that the complex [CdL1(NO3 )].NO3 contains a hexadentate macrocyclic ligand and a bidentate NO3 − anion with an eight-coordinated cadmium in distorted dodecahedron geometry. The molecular structures of the complexes [Cd2 (L3O)(NO3 )3 (H2 O)] and [Cd2 (L4O)(NO3 )3 ], on the other hand, exhibit of two seven-coordinated cadmium centers, which are bridged by the deprotonated hydroxyl group. The coordination geometries of the cadmium ions can be described as a capped trigonal prism and/or capped octahedron. Keywords: Aza-Crown Ligands, Cadmium, Macrocyclic Chemistry, Schiff base, Template Condensation

1

1. Introduction

2

Functionalized macrocyclic compounds play an important role in mul-

3

tiple fields of host-guest chemistry and molecule recognition as e.g. recep-

4

tors for cationic, anionic, and neutral guests [1, 2, 3, 4]. For ideal molecule

5

recognition a diversity of different macrocyclic compounds is needed, thus

6

expansion of our fundamental understanding of the macrocyclization pro-

7

cesses is essential for the synthesis of such compounds. One of the classical

8

reactions used to form macrocycles with nitrogen donor atoms is Schiff base

9

condensation. The classical Schiff condensation using monocarbonyl com-

10

pounds and monoamines as the starting compounds occurs with high yields.

11

The reaction of dicarbonyl compounds with diamines is however much more

12

complicated and can produce a wide range of products (Fig. 1). This re-

13

action, when carried out with a 1:1 molar ratio of diamine and dicarbonyl,

14

will yield [1+1]-condensation macrocyclic products I or acyclic products II. 2

15

The latter can react with another dicarbonyl compound or diamine to give

16

the [2+1]-condensation product III or the [1+2]-condensation product IV,

17

respectively. Compounds III and IV are capable of further reacting with

18

yet another diamine and dicarbonyl compounds, respectively, to produce the

19

[2+2]-macrocycle V as well as linear oligomers VI. In some cases formation

20

of products with a larger macrocyclic core (e.g., [3+3]-, [4+4]-, [5+5]-, [6+6],

21

and even [7+7]-condensation products) was observed [5]. Clean formation of

22

only one of the products I-V can rarely be obtained under standard reaction

23

conditions. Introduction of a template agent is the most reliable method to

24

prevent oligocondensation and steer the condensation process towards forma-

25

tion of macrocyclic Schiff bases, I and V. The use of metal ions with different

26

ionic radii coordination requirements [6], pendant armed amins and solvents

27

[7, 8] make it possible to somewhat control and predict the nature of the

28

product formed . As polydentate ligands, compounds I-V can tightly bind

29

with metal ions and can form bi- and polynuclear complexes in which two or

30

more metal atoms are placed in close proximity to each other. These types of

31

complexes might, depending on the nature of the metal ion, exhibit unusual

32

magnetic properties [9, 10] and catalytic activity [11].

33

In our previous investigations we had been used 2-[3-(2-formylphenoxy)-

34

2-hydroxypropoxy] benzaldehyde (PL) as a dicarbonyl precursor in the tem-

35

plate synthesis of nickel complexes of macrocyclic Schiff base ligands that

36

incorporate mixed donor atoms with one and two pendant alcohol functions

37

[12, 13]. Condensation of PL with 1,3-diaminopropane and 2-hydroxy-1,3-

38

diaminopropane in the presence of different nickel(II) salts yielded mononu-

39

clear 16-membered [1+1] macrocyclic nickel complexes in high yield. Our

3

40

attempts to synthesize nickel(II) complexes by condensation of diethylen-

41

etriamine, 1,2-diaminoethane, and 1,2-diaminobenzene with PL were not

42

successful [14]. On the other hand, Zn(II) template condensation of PL

43

with 1,2-diaminoethane and 1,2-diaminopropane resulted in binuclear com-

44

plexes of [1+2] acyclic Shiff-base ligands [15]. In continuation of this re-

45

search on effect of transition metal radii and diamine chain-spacer, we would

46

like to report the cadmium(II) templated synthesis of four new Schiff base

47

ligands, [1+1] macrocyclic ligands L1OH and L2OH and [1+2] acyclic lig-

48

ands L3O− and L4O− (Fig. 2). Synthesis, characterization and X-ray crys-

49

tal structures of the mononuclear cadmium macrocyclic Schiff base complex

50

[Cd(L1OH)(NO3 )]NO3 and the dinuclear cadmium acyclic Schiff base com-

51

plexes [Cd2 (L3O)(NO3 )3 (H2 O)] and [Cd2 (L4O)(NO3 )3 ] are reported.

52

2. Experimental

53

2.1. Materials and Physical Measurements

54

2-[3-(2-Formylphenoxy)-2-hydroxypropoxy] benzaldehyde (PL) was pre-

55

pared using a procedure similar to the reported method using salicylaldehyde

56

and 1,3-dichloro-2-propanol [12]. Other reagents were purchased from Merck

57

or Fluka and were used without further purification. Solvents were dried and

58

purified before being used according to published procedures [16].

59

Elemental analyses were performed with an elemental analyzer Elementar

60

Vario El III. All melting points were taken using an Electrothermal IA 9100

61

apparatus in open capillary tubes and are uncorrected. Infrared spectra were

62

recorded on a Shimadzu FT-IR 8400 instrument as KBr pellets. Conductance

63

measurements were performed using a Metrohm 712 Conductometer for ca. 4

Figure 1: Scheme condensation products of dicarbonyls with diamines [6].

Figure 2: A scheme condensation products of cadmium templated synthesis.

5

64

10−3 M solutions of the complexes in methanol at 25◦ C. UV-Vis spectra

65

were obtained from a Shimadzu UV-1601PC spectrometer for ca. 10−5 M

66

solutions of the complexes in methanol.

67

2.2. Synthesis

68

1. Synthesis of [Cd(L1OH)(NO3 )]NO3

69

A methanol solution (100 mL) of diethylenetriamine (0.306 g, 2.97

70

mmol) was added with stirring to a 200 mL hot methanol solution

71

of PL (0.918 g, 2.97 mmol) and Cd(NO3 )2 ·4H2 O (0.945 g, 2.97 mmol).

72

The solution was stirred and refluxed for 2 h. The volume was re-

73

duced to 100 mL using a rotary evaporator. Colorless crystals were

74

formed after several days and recrystallized from a mixture of methanol

75

and 1-butanol. The resulting plate-like crystals were collected by fil-

76

tration and dried in a vacuum desiccator over P4 O10 . Yield 0.821 g

77

(46%). The compound decomposes above 238 ◦ C and shows no melt-

78

ing point. Anal. Calc. (Found) for C21 H25 CdN5 O9 (F.W.= 603.82): C,

79

41.77 (42.09); H, 4.17 (4.34); N, 11.60 (11.41)%. Selected FT-IR data,

80

(cm−1 ): 3448w, 3259w, 2920w, 1647s (C=N), 1600s, 1575m, 1492m,

81

1355s, 1220s, 1112m, 1031s, 763m, 445w. Λm (CH3 OH): 110 S cm2

82

mol−1 .

83

2. Synthesis of Cd(L2OH)(NO3 )2

84

Using the same method as for [Cd(L1OH)(NO3 )]NO3 a methanol solu-

85

tion (100 mL) of dipropylenetriamine (0.423 g, 3.22 mmol) was added

86

with stirring to a 200 mL hot methanol solution of PL (0.966 g, 3.22

87

mmol) and Cd(NO3 )2 ·4H2 O (0.993 g, 3.22 mmol). The solution was

88

stirred and refluxed for 2 h. The volume was reduced to 100 mL us6

89

ing a rotary evaporator. The white residue that appeared after several

90

days was collected by filtration and dried in a vacuum desiccator over

91

P4 O10 . Yield 0.612 g (30%). The compound decomposes above 245◦ C

92

and shows no melting point. Anal. Calc. (Found) for C23 H29 CdN4 O6

93

(F.W.= 631.916): C, 43.72 (43.57); H, 4.63 (4.40); N, 11.08 (10.80)

94

%. Selected FT-IR data, (cm−1 ): 3442w, 3259m, 2927w, 2856w, 1637s

95

(C=N), 1600s, 1490s, 1382s, 1240s, 757m, 441w.

96

3. Synthesis of [Cd2 (L3O)(NO3 )3 (H2 O)]

97

A methanol solution (60 mL) of 1,2-diaminoethane (0.264 g, 4.39 mmol)

98

was added slowly with stirring to a 200 mL hot methanol solution of

99

PL (1.321 g, 4.39 mmol) and Cd(NO3 )2 · 4H2 O (1.356 g, 4.39 mmol).

100

The solution was stirred and refluxed for 2 h. The volume was re-

101

duced to 100 mL using a rotary evaporator. The resultant white solid

102

product was collected by filtration and recrystallized from a mixture

103

of methanol and 1-butanol. The resulting plate-like colorless crystals

104

were filtered off and dried in a vacuum desiccator over P4 O10 . Yield

105

1.139 g (32% based on PL). The compound decomposes above 240◦ C

106

and shows no melting point. Anal. Calc. (Found) for C21 H29 Cd2 N7 O13

107

(F.W.= 812.316): C, 31.05 (31.25); H, 3.60 (3.70); N, 12.07 (11.63)

108

%. Selected FT-IR data, (cm−1 ): 3421w, 3338m, 3278m, 2943w, 1645s

109

(C=N), 1598s, 1492m, 1384s, 1230m, 1035m, 999m, 796m, 437w. Λm

110

(CH3 OH): 165 S cm2 mol−1 .

111

4. Synthesis of [Cd2 (L4O)(NO3 )3 ]

112

Using the same method as for [Cd2 (L3O)(NO3 )3 (H2 O)] a methanol so-

113

lution (60 mL) of 1,2-diaminopropane (0.270 g, 3.64 mmol) was added 7

114

with stirring to a 200 mL hot methanol solution of PL (1.09 g, 3.64

115

mmol) and Cd(NO3 )2 ·4H2 O (1.125 g, 3.64 mmol). The solution was

116

stirred and refluxed for 2 h. The volume was reduced to 100 mL using

117

a rotary evaporator. Colorless crystals formed after 10 days and were

118

recrystallized from methanol by slow evaporation. The resulting plate-

119

like crystals were collected by filtration and dried in a vacuum desic-

120

cator over P4 O10 . Yield 0.944 g (32 % based on PL). The compound

121

decomposes above 209◦ C and shows no melting point. Anal. Calc.

122

(Found) for C23 H31 Cd2 N7 O12 (F.W.= 822.354): C, 33.59 (33.25); H,

123

3.80 (3.70); N, 11.92 (11.63) %. Selected FT-IR data, (cm−1 ): 3425w,

124

3321s, 3259s, 2925m, 1649s (C=N), 1598s, 1494s, 1442s, 1303s, 1230s,

125

1132s, 983s, 912m, 752m, 416w. Λm (CH3 OH): 155 S cm2 mol−1 .

126

2.3. Crystal growth and X-ray diffraction

127

Colorless crystals of [Cd(L1OH)(NO3 )]NO3 and [Cd2 (L3O)(NO3 )3 (H2 O)]

128

were obtained from a (1:1) mixture solution of methanol/1-butanol and crys-

129

tals of [Cd2 (L4O)(NO3 )3 ] from methanol by slow evaporation. Data were col-

130

lected at 100 K using the Apex2 suite of programs on a Bruker Smart APEX

131

CCD diffractometer with monochromated Mo Kα radiation (λ = 0.71073˚ A)

132

using the ω scan mode [17]. Cell refinement, data reduction and absorption

133

corrections were carried out using APEX2. The structure of [CdL1(NO3 )].

134

NO3 was solved by charge flipping in Superflip [18] and refined by full-

135

matrix least-squares calculations on F with Jana2006 [19]. The structures of

136

[Cd2 (L3O)(NO3 )3 (H2 O)] and [Cd2 (L4O)(NO3 )3 ] were solved by direct meth-

137

ods using Shelxtl 6.14 and were refined by full-matrix least-squares calcu-

138

lations on F2 with Shelxtl 6.14 [20, 21]. All H atoms (except H atoms of 8

139

water for [Cd2 (L3O)(NO3 )3 (H2 O)]) were placed in calculated positions (CH

140

= 0.99 ˚ A, NH = 0.92 ˚ A) and were refined using a riding model with an

141

isotropic displacement parameter 1.5 (methyl) or 1.2 times (all others) that

142

of their carrier atoms. Water hydrogen atoms were located in difference den-

143

sity Fourier maps and were refined with an OH distance of 0.84(2) ˚ A and

144

an isotropic displacement parameter of 1.5 times that of the adjacent oxygen

145

atom.

146

Anions in crystal structure of [Cd(L1OH)(NO3 )]NO3 , exhibit severe dis-

147

order. The fourfold disordered nitrate anion has been described by a molec-

148

ular approach as available in Jana2006. Pseudo-rigid body refinement of

149

four-fold disordered anion is described in appendix A. The positions of Cd1

150

and O2 atoms in the ring were partially disordered. Details of the X-ray

151

experiments and crystal data are summarized in Table 1.

9

Table 1: Crystal data and refinement details at T = 100(2) K Chemical formula

[Cd(L1OH)(NO3 )]NO3

[Cd2 (L3O)(NO3 )3 (H2 O)]

[Cd2 (L4O)(NO3 )3 ]

C21 H25 Cd N4 O6, 0.5(N2 O6)

C21 H29 Cd2 N7 O13

C23 H31 Cd2 N7 O12

Formula weight

603.9

812.31

822.35

Cell setting, Space group

Monoclinic, C2/c

Triclinic, P¯1

Triclinic, P¯1

a (˚ A)

30.769(9)

8.809(4)

11.9012(6)

b (˚ A)

9.639(3)

13.312(6)

12.0885(11)

c (˚ A)

22.180(6)

13.499(10)

12.3069(6)

108.135(9)

96.9260(10)

α (◦) β (◦)

132.343(3)

γ (◦)

95.729(9)

117.1710(10)

108.551(6)

106.1060(10)

10

V (˚ A3 )

4862(2)

1390.9(14)

1448.64(17)

Z

8

2

2

Dcalc (g cm−3 )

1.650

2

2

Crystal size (mm3 )

0.20 × 0.17 × 0.11

0.69 × 0.08 × 0.02

0.35 × 0.33 × 0.15

Crystal form, color

Platelet, colourless

Platelet, colourless

Platelet, colourless

Range of h

-43 to 44

-11 to 11

-15 to 15

Range of k

-13 to 13

-17 to 17

-16 to 16

Range of l

-31 to 30

-17 to 17

-16 to 16

Absorption corr.

Multi-scan

Multi-scan

Multi-scan

Tmin , Tmax

0.673, 0.746

0.452, 0.965

0.665,0.791

Measured & Observed

26676, 6473

13905, 5560

14819, 6438

Rint

0.021

0.038

0.026

Criterion for observed reflection

I > 3σ(I)

I > 2σ(I)

I > 2σ(I)

GOF

3.91

1.04

1.02

R(obs ), wR(all )

0.0470, 0.0711

0.038, 0.102

0.026, 0.064

No. of parameters

364

394

399

-1.15, 2.39

1.94, -1.46

1.84, -0.77

No. of reflections

∆ρmax , ∆ρmin

(e ˚ A−3 )

152

3. Results and discussion

153

3.1. Syntheses and characterization

154

When treating equimolar amounts of diethylenetriamine or dipropylene-

155

triamine, dialdehyde PL and Cd(NO3 )2 ·4H2 O in a diluted boiling methanol

156

solution (ca. 0.01-0.02 M) for two hours, the respective [1+1] macrocyclic

157

Schiff base complexes [Cd(L1OH)(NO3 )]NO3 and Cd(L2OH)(NO3 )2 were ob-

158

tained. Complete conversion was checked using IR spectroscopy. Dialdehyde

159

PL shows a carbonyl mode at 1679 cm−1 , which was absent in the FT-IR

160

of the complexes formed. Amine NH2 bands were also absent and instead

161

strong C=N bands at 1647 and 1637 cm−1 were observed consistent with the

162

formation of imine (C=N) linkages and formation of a macrocyclic ligand.

163

Cd(II) ion template condensation of PL with the shorter spacers di-

164

amines, 1,2-diaminopropane and 1,2-diaminoethane, on the other hand, imi-

165

tates Zn(II) template ion [15]. The dialdehyde PL reacted with two molecules

166

of diamine, forming acyclic Schiff base ligands (L3O− and L4O− ). The re-

167

actions proceeded through a [1+2]-condensation leading to the formation of

168

acyclic ligands. This is especially noteworthy as the clean formation of pure

169

[1+2]-condensation blocks which usually requires special developed methods

170

[22, 23]. Acyclic condensation products are usually only formed if a 2:1

171

stoichiometric ratio of reactants is used. Also, condensation of PL with 1,2-

172

diaminoethane and 1,2-diaminopropane (in a 1:1 molar ratio) in presence of

173

same molar ratio of cadmium(II) does however solely give [1+2]-condensation

174

products [Cd2 (L3O)(NO3 )3 (H2 O)], and [Cd2 (L4O)(NO3 )3 ] as the only iso-

175

lated products with lower yield.

176

This is in contrast to previous work with nickel as the templating agent di11

177

aldehyde PL produced neither macrocyclic nor acyclic Schiff bases complexes

178

upon treatment with 1, 2-diaminoethane and 1,2-diaminopropane under the

179

same conditions [12, 13, 14], that emphasize the effect of templating metal.

180

Zn(II) and Cd(II) by virtue of their similar electronic structures distinct

181

from other transition metals. Similar products via Cd(II) and Zn(II) ions as

182

templating agent may show misstep metal selectivity in physiological roles.

183

After the successful reactions using amines with each two primary amine

184

groups we investigated if the condensation reactions could be expanded to

185

the even longer spacers or to spacers with three primary amine groups. Tri-

186

ethylenetetraamine and tris(2-aminoethyl)amine were used in these reactions.

187

Our attempts to isolate cadmium(II) macrocycles or non-macrocycles Schiff

188

base complexes were, however, unsuccessful. Termination of the condensation

189

reactions actually proved not to be the problems, but instead condensation

190

reactions did not occur at all and the reaction of PL with those tetraamines

191

leads to the formation of adducts of cadmium with only tetraamine in which

192

the tetraamine ligands chelate to cadmium. In the case of using tris(2-

193

aminoethyl)amine, fine colorless crystals are formed immediately after ad-

194

dition of the amine to a methanol solution of PL and cadmium(II). X-ray

195

crystal structure analysis of the reaction product confirms the formation of a

196

(2:2) adduct of tris(2-aminoethyl)amine with Cd(NO3 )2 , which was reported

197

previously [24].

198

The molar conductivity for ca. 10−3 M of [Cd(L1OH)(NO3 )]NO3 in

199

methanol solution at 25◦ C is in accordance with that expected for 1:1 elec-

200

trolyte (80-110 S cm2 mol−1 ). Therefore, counter ions dissociates in solution.

201

The measured values for [Cd2 (L3O)(NO3 )3 (H2 O)], and [Cd2 (L4O)(NO3 )3 ]

12

Table 2: The UV-Vis electronic absorptions (λmax , nm) in CH3 OH at room temperature.

Complex

π→ π ∗

n→ π ∗

[[Cd(L1OH)(NO3 )]NO3

215, 251

308

[Cd2 (L3O)(NO3 )3 (H2 O)]

208, 251

307

[Cd2 (L4O)(NO3 )3 ]

208, 253

307

202

under the same conditions are as expected for a 2:1 electrolyte (160-220 S cm2

203

mol−1 ) [25]. These observations imply that at least one of the nitrate ions in

204

[Cd2 (L3O)(NO3 )3 (H2 O)] and [Cd2 (L4O)(NO3 )3 ] is tightly coordinated to the

205

cadmium ion. The Cd(L2OH)(NO3 )2 complex does not solvate in methanol.

206

Complexes provide a unique opportunity to investigate the photophysical

207

properties of a series of Cd complexes with Schiff-base ligands that containing

208

imine C=N groups. Electronic absorption data for [Cd(L1OH)(NO3 )]NO3 ,

209

[Cd2 (L3O)(NO3 )3 (H2 O)] and [Cd2 (L4O)(NO3 )3 ] are tabulated in Table 2.

210

The UV-Vis spectra of measured in CH3 OH show two absorptions bands

211

ranging in 200–260 nm and tailing to a weak absorbtion band in region 250-

212

360 nm. Based on the absorption bands occurring in the similar spectral

213

region, these absorptions are most likely ascribed to aromatic π→ π ∗ and

214

imine n→ π ∗ transitions respectively.

215

3.2. Crystal Structures

216

The structure of the [Cd(L1OH)(NO3 )]NO3 complex is illustrated in Fig.3

217

and Tables 3 ( also see appendix B) gives bond lengths and angles. The X-ray

218

structure confirms the results from IR spectroscopy analysis and demonstrate

219

that the metal cation has been incorporated upon complexation to generate

220

an endomacrocyclic complex with a ligand cavity occupied by the Cd(II) 13

(b)

(a)

Figure 3: (a) Molecular structure of the [Cd(L1OH)(NO3 )]NO3 and (b) fourfold disordered [NO3 ]− ion. Thermal ellipsoids are drawn with 50% probability.

221

ion. The disordered cadmium ion is bound to all six nitrogen and oxygen

222

donor atoms: the three nitrogen and two ether oxygen donor atoms of the

223

macrocyclic backbone and to the oxygen atom of the hydroxyl pendant arm.

224

In addition to the six donor atoms of L1OH, a bidentate nitrate ion is also

225

coordinated to the cadmium which is accordingly eight-coordinate.

226

The coordination geometry around the cadmium cation is best described

227

as a distorted dodecahedron (Fig.4.a). In the description of an eight-coordinate

228

polyhedron, the best criterion for assignment as dodecahedral is the occur-

229

rence of the two orthogonal planar trapezoids required of point group D2 d

230

[26]. The two interpenetrating trapezoids, which characterize the dodecahe-

231

dron, are defined by the positions of the atoms O1, O3, N3, and N1 and by 14

Table 3: Selected bond lengths (˚ A) and bond angles (◦) for [Cd(L1OH)(NO3 )]NO3

Bond Lengths (˚ A) Cd1a–N1

2.334(6)

Cd1a–O2a

2.335(13)

Cd1a–N2

2.367(4)

Cd1a–O3

2.458(3)

Cd1a–N3

2.404(5)

Cd1a–O4

2.317(3)

Cd1a–O1

2.528(4)

Cd1a–O5

2.648(3)

O2a–Cd1a–N1

103.0(5)

O1–Cd1a–O3

69.18(11)

N3–Cd1a–N1

147.0(10)

O1–Cd1a–O5

120.42(8)

N2–Cd1a–N1

74.82(16)

O3–Cd1a–O5

113.41(9)

N3–Cd1a–O1

71.0(10)

N3–Cd1a–N2

73.01(15)

O2a–Cd1a–O5

170.3(4)

N1–Cd1a–O3

72.15(11)

N3–Cd1a–O3

140.14(11)

O4–Cd1a–O3

75.52(9)

N3–Cd1a–O5

85.63(12)

O4–Cd1a–O1

76.26(10)

O2a–Cd1a–O3

76.0(4)

O4–Cd1a–N1

102.11(3)

O4–Cd1a–O2a

137.7(3)

O4–Cd1a–N2

129.30(10)

N1–Cd1a–O1

140.41(11)

O4–Cd1a–N3

93.76(12)

N1–Cd1a–O5

82.71(11)

O4–Cd1a–O5

50.83(7)

N2–Cd1a–O1

136.88(15)

N2–Cd1a–O3

142.48(14)

N2–Cd1a–O5

79.02(9)

O2a–Cd1a–N2

94.8(3)

O2a–Cd1a–N3

84.4(5)

O2a–Cd1a–O1

59.7(3)

Bond Angles (◦ )

15

O1

O3 N3

N1

N2 O5

(b)

(a)

(c)

Figure 4: Possible coordination geometries around cadmium ion.(a) Dodecahedral geometry around cadmium in the [Cd(L1OH)(NO3 )]NO3 complex. (b) Capped trigonal prism, (c) distorted capped octahedral coordinations in the [Cd2 (L3O)(NO3 )3 (H2 O)] complex.

232

O2 (disordered), O4, O5, and N2. The angle between the mean planes of

233

these trapezoidal planes is 88.56◦ , very close to the ideal one (90◦ ). The two

234

phenyl rings are inclined with respect to the mean plane through the N3 O2

235

backbone donor set of the macrocycle by 33.94 and 28.51 ◦ .

236

In the crystal structure of [Cd(L1OH)(NO3 )]NO3 there are intermolecular

237

O–H· · ·(O/N)nitrate H-bonds (hydrogen bonds) that connect each complex via

238

disordered O2–H2 hydrogen donors to four-fold disordered O or N acceptors

239

of nitrate. N–H· · ·(O/N)nitrate H-bonds connect each complex via amine

240

hydrogen donors (N2–H2n) to O or N atoms of four-fold disordered nitrate.

241

Phenyl ring (I), defined by C16, C17, C18, C19, C20 and C21 atoms exhibits

242

a slipped π· · ·π contact with the phenyl ring (II) defined by C4, C5, C6, C7,

243

C8 and C9 atoms, with a Center(I)· · · Center(II) distance of phenyl rings

244

4.062(2) ˚ A and perpendicular distance of phenyl ring (I) on phenyl ring (II) 16

π−π

π−π

N/O−H···N/O

π−π

π−π

Figure 5: Hydrogen bonds between the [Cd(L1OH)(NO3 )]+ and the disordered anions [NO3 ]− along a axis. π–π interactions contact phenyl rings in such a way that macrocylic molecules are stacking and running along b axis. The O-H· · ·O, N-H· · ·N and N–H· · ·O H-bonds contact complex to disordered nitrate.

245

3.44 ˚ A which are typical of π· · ·π contacts as defined by Janiak [27]. Weak

246

C–H· · ·O H-bonds lead to the formation of macroclyclic molecular stacks

247

with the voiders between them that is filled with disordered nitrate anion see

248

Fig. 5. The significant hydrogen bonding interactions are given in Table 4

249

and appendix B.

250

The structure of the complex [Cd2 (L3O)(NO3 )3 (H2 O)] is illustrated in

251

Fig. 6. a. and Table 5 gives bond lengths and angles. The structure exhibits

17

Table

4:

Geometry

of

selected

strong

intermolecular

hydrogen

bonds

[Cd(L1OH)(NO3)]NO3 .

D-H· · · A

d(D-H) d(H· · · A)

d(D· · · A)

∠D–H· · ·A

(˚ A)

(˚ A)

(˚ A)

(deg)

N2–H2n· · · O1b

0.92

2.36

3.179(19)

148.54

N2–H2n· · · O2b

0.92

2.10

2.97(2)

156.63

N2–H2n· · · N1b

0.92

2.44

3.330(14)

161.68

O2a –H2a· · · O3a

0.85(4)

1.76(6)

2.548(15)

152(9)

O2a –H2a· · ·O2c

0.85(4)

1.89(8)

2.56(4)

135(9)

O2a –H2a· · ·O3c

0.85(4)

2.34(6)

2.88(2)

122(6)

O2a –H2a· · ·N1c

0.85(4)

2.38(7)

3.093(18)

141(8)

O2a –H2a· · ·O2d

0.85(4)

1.73(11)

2.17(5)

109(8)

O2a –H2a· · ·O3d

0.85(4)

2.06(5)

2.90(3)

169(9)

O2a –H2a· · ·N1d

0.85(4)

1.92(7)

2.58(2)

134(8)

18

for

252

two seven coordinated cadmium ions with different coordination geometries.

253

Each Cd2+ is coordinated by three donor atoms of the [1+2] non-macrocylic

254

ligand, and one bridging alkoxide oxygen. In addition, one asymmetrically

255

bonded bidentate nitrate, and one water molecule are coordinated to Cd1;

256

one monodentate nitrate and one asymmetrically bonded bidentate nitrate

257

are completing the coordination sphere of Cd2. The construction of [1+2]

258

non-macrocylic ligand is similar to the condensation product in presence of

259

Zn(II) ion [15]. The coordination polyhedron around Cd1 can be described as

260

a capped trigonal prism (Fig.4.b) with near C2 V point group symmetry. The

261

trigonal faces of the prism are composed of two parallel planes with a small

262

twist angle of 5.33(15)◦ which is close to the value in an ideal trigonal prism

263

(0◦ ) [26] and formed by N3, O10, and O3 and by O13, O2, and N4, while

264

O12 is capping one of the square faces of the trigonal prism. In contrast Cd2

265

exhibits a distorted capped octahedral coordination with N1, N2, O1, and O2

266

occupying the approximate equatorial plane (rms deviation from planarity

267

for these atoms is 0.1154 ˚ A), Fig.4.c. The axial sites are occupied by one

268

oxygen atom from a monodentate nitrate ligand and one oxygen atom of a

269

very asymmetrically bonded bidentate nitrate ligand while a second oxygen

270

atom of that nitrate acts as a capping atom , Fig.4.c. The two phenyl rings

271

are nearly in plane with each other with an angle of only 11.68 (0.19)

272

The Cd1· · ·Cd2 distance within the complex is 3.854 ˚ A. The Cd–O(alkoxide)

273

distance are shorter at 2.160(3) and 2.218(3)˚ A as a result of the negative

274

charge of the alkoxide group.

◦

.

275

In the crystal structure of [Cd2 (L3O)(NO3 )3 (H2 O)] there are two inter-

276

molecular O–H· · ·O hydrogen bonds (O13–H13B· · ·O5 and O13–H13B· · ·O6)

19

(b)

(a)

Figure 6: Molecular structures of (a)[Cd2 (L3O)(NO3 )3 (H2 O)] and (b) [Cd2 (L4O)(NO3 )3 ] with the atom labels as employed in the present work. Thermal ellipsoids are drawn with 50% probability.

O−H···O

N−H···O

O−H···O

CH − π π−π

O−H···O N−H···O

N−H···O

O−H···O

Figure 7: Crystal packing in [Cd2 (L3O)(NO3 )3 (H2 O)]. Each zigzag chain constructed by O-H· · ·O and N–H· · ·O H-bonds shown in orange and blue chains. CH· · ·π and π–π interactions connect two neighboring zigzag shaped chains.

20

Table 5: Selected bond lengths (˚ A)and bond angles (◦ ) for [Cd2 (L3O)(NO3 )3 (H2 O)]

Bond Lengths (˚ A) Cd1–O2

2.218(3)

Cd2–O2

2.160(3)

Cd1–O3

2.532(3)

Cd2-O1

2.538(3)

Cd1–N3

2.333(4)

Cd2-N2

2.291(3)

Cd1–N4

2.315(3)

Cd2-N1

2.295(3)

Cd1–O13

2.358(3)

Cd2-O4

2.562(3)

Cd1–O10

2.374(3)

Cd2-O8

2.486(3)

Cd1–O12

2.608(3)

Cd2-O7

2.503(3)

N4-Cd1-N3

76.19(12)

N2-Cd2-N1

76.98(12)

N3-Cd1-O3

69.45(9)

N2-Cd2-O1

71.47(10)

O2-Cd1-O3

71.69(10)

O2-Cd2-O1

73.96(9)

O2-Cd1-N4

98.99(11)

O2-Cd2-N1

134.78(11)

O10-Cd1-O12

51.63(8)

O8-Cd2-O7

51.53(9)

O13-Cd1-O10

80.57(10)

O8-Cd2-O4

168.88(9)

O13-Cd1-O12

74.45(10)

O7-Cd2-O4

138.01(9)

Bond Angles (◦ )

21

277

that arise from the coordinated water molecule to oxygen atoms of the mon-

278

odentate nitrate ion (O5 and O6) in a neighboring molecule. Four inter-

279

molecular N–H· · ·O hydrogen bonds (N1–H1D· · ·O12, N1–H1D· · ·O13, N4–

280

H4A· · ·O7, and N4–H4A· · ·O9) connect each complex via amine hydrogen

281

donors (N1 and N4) to water and nitrate O acceptor atoms. One C–H· · ·π

282

contact is observed between H3 and the π system of a phenyl ring (I) defined

283

by C13, C14, C15, C16, C17, and C18 with an H3· · ·Center distance of 2.836

284

˚ A. The other face of the same phenyl ring(I) exhibits a slipped π· · ·π contact

285

with the other phenyl ring (II) defined by C4, C5, C6, C7, C8 and C9, with

286

a Center(I)· · ·Center(II) phenyl rings distance of 4.201 ˚ A and an interplanar

287

distance around 3.4 ˚ A. The distances between some of atoms C8–C14, C8–

288

C15, and C7–C15 are 3.361, 3.476 and 3.497 ˚ A. The above interactions and

289

two weak C–H· · ·O hydrogen bonds (C7–H7· · ·O11 and C10–H10· · ·O4) lead

290

to the formation of sheets of molecules (Fig.7). The list of H-bonds are given

291

in Table 6.

292

The structure of the [Cd2 (L4O)(NO3 )3 ] complex is illustrated in Fig. 6.b

293

and Table 7 gives bond lengths and angles. The structure of this complex

294

and that of [Cd2 (L3O)(NO3 )3 (H2 O)] are somewhat similar with same crystal

295

system and space group and consisting in both case of complexes with two

296

seven coordinated cadmium centers. Also, the construction of [1+2] non-

297

macrocylic ligand, crystal system and space group are similar to the same

298

condensation reaction via Zn(II) template ion [15]. In [Cd2 (L4O)(NO3 )3 ]

299

each Cd2+ is coordinated by three donor atoms of the [1+2] non-macrocylic

300

ligand, one bridging alkoxide oxygen, and one oxygen atom of an exogenous

301

1,3-brideging nitrate. In addition, one asymmetrically bonded bidentate ni-

22

Table 6: Geometry of intermolecular hydrogen bonds for [Cd2 (L3O)(NO3 )3 H2 O].

D-H· · · A

d(D-H)

d(H· · · A)

d(D· · · A)

∠D–H· · ·A Symmetry codes

(˚ A)

(˚ A)

(˚ A)

(deg)

N1–H1C· · · O5

0.92

2.21

3.059(5)

154

N1–H1D· · · O12

0.92

2.49

3.217(5)

136

-x, 1-y, 1-z

N1–H1D· · · O13

0.92

2.27

3.046(5)

142

-x, 1-y, 1-z

N4–H4A· · · O7

0.92

2.26

3.145(5)

161

-x, 1-y, 1-z

N4–H4A· · · O9

0.92

2.52

3.311(6)

145

-x, 1-y, 1-z

N(4)–H4B· · · O4

0.92

2.50

3.205(6)

134

N(4)–H4B· · · O5

0.92

2.55

3.317(6)

141

O13–H13A· · · O7

0.84(3)

1.92(3)

2.752(4)

178(7)

O13–H13B· · · O5

0.84(4)

2.01(3)

2.829(5)

166(5)

1+x, y, z

O13–H13B· · · O6

0.84(4)

2.49(5)

3.146(5)

137(4)

1+x, y, z

C7–H7· · · O11

0.95

2.59

3.433(6)

148

1-x, 2-y, 1-z

C10–H10B· · · O4

0.99

2.37

3.330(6)

164

-x, 2-y,1-z

C19–H19· · · O11

0.95

2.45

3.392(5)

170

-x, 1-y, -z

23

302

trate ion also coordinates to each of the cadmium ions.

303

The coordination geometry around each cadmium is a distorted capped

304

octahedron, where the N2 O2 backbone donor set of L4O− occupies the equa-

305

torial plane for each cadmium center. The mean plane around the Cd1 as

306

defined by Cd1, N3, N4, O2, and O1 is distorted with a rms deviation from

307

planarity of 0.1399 ˚ A, and the mean plane around Cd2 which is defined by

308

Cd2, N2, N1, O2, and O3, is distorted with a rms deviation from planarity of

309

0.1520 ˚ A. The axial sites are occupied by one oxygen atom of a 1,3-bridging

310

nitrate and one oxygen atom of a very asymmetrically bonded bidentate ni-

311

trate ligand while a second oxygen atom of that nitrate acts as a capping

312

atom. The two phenyl rings are almost parallel with an interplanar angle of

313

only 7.90 ◦ . The Cd1· · ·Cd2 distance is 3.547 ˚ A.

314

In the crystal structure of [Cd2 (L4O)(NO3 )3 ] four N–H· · ·O hydrogen

315

bonds (N2-H2A· · ·O12, N2-H2B· · ·O5, N3-H3C· · ·O6, N3-H3D· · ·O12) and

316

one C-H· · ·O interaction (C12-H12· · ·O9) stabilize an one dimensional ar-

317

rangement of complex molecules along the a axis of the crystal (Fig. 8). Each

318

of the chains of molecules is parallel to another chain of hydrogen-bonded

319

cadmium complexes. Weak intermolecular C-H· · ·O hydrogen bonds (C6-

320

H6· · ·O12, C10-H10· · ·O9, C16-H16B· · ·O7, C16-H16B· · ·O9, C20-H20· · ·O7,

321

C23-H23· · ·O4) and C-H· · ·π, π–π contacts are extended in other directions.

322

A C-H· · ·π contact is observed between C2-H2 and the π system of the phenyl

323

ring (I) defined by C4, C5, C6, C7, C8, and C9 with a H2· · ·Center distance

324

of 2.985 ˚ A (Fig. 8). The other face of the phenyl ring exhibits a slipped π–π

325

contact with the other phenyl ring (II) defined by C18, C19, C20, C21, C22,

326

and C23, with a Center (I)· · ·Center (II) distance of 4.234 ˚ A and an inter-

24

Table 7: Selected bond lengths (˚ A)and bond angles (◦) for [Cd2 (L4O)(NO3 )3 ]

Bond Lengths (˚ A) Cd1–O2

2.1490(16)

Cd2–O2

2.1437(16)

Cd1–O1

2.5131(16)

Cd2-O3

2.5439(16)

Cd1–N4

2.275(2)

Cd2-N1

2.272(2)

Cd1–N3

2.258(2)

Cd2-N2

2.269(2)

Cd1–O10

2.5604(17)

Cd2-O11

2.6367(17)

Cd1–O7

2.3700(19)

Cd2-O5

2.5233(18)

Cd1–O8

2.637(2)

Cd2-O4

2.394(2)

N3-Cd1-N4

78.10(7)

N2-Cd2-N1

78.11(7)

N4-Cd1-O1

74.78(6)

N1-Cd2-O3

72.94(6)

O2-Cd1-O1

73.45(7)

O2-Cd2-O3

71.83(6)

O2-Cd1-N3

127.56(7)

O2-Cd2-N2

130.49(7)

O7-Cd1-O8

50.57(7)

O4-Cd2-O5

51.95(6)

O7-Cd1-O10

156.38(7)

O4-Cd2-O11

157.13(6)

O10-Cd1-O8

152.52(6)

O5-Cd2-O11

154.83(6)

Bond Angles (◦ )

25

Table 8: Geometry of intermolecular hydrogen bonds for [Cd2 (L4O)(NO3 )3 ].

D-H· · · A

d(D-H)

d(H· · · A)

d(D· · · A)

∠D–H· · ·A Symmetry codes

(˚ A)

(˚ A)

(˚ A)

(deg)

N2–H2A· · · O12

0.92

2.23

3.146(3)

176

2-x, -y, -z

N2–H2B· · · O5

0.92

2.22

3.124(4)

166

1-x, -y, -z

N3–H3C· · · O6

0.92

2.19

2.977(3)

144

1-x, -y, -z

N3–H3D· · · O12

0.92

2.07

2.969(3)

165

2-x, -y, -z

C6–H6· · · O12

0.95

2.55

3.188(3)

125

2-x, 1-y, -z

C10–H10· · · O9

0.95

2.51

3.384(4)

153

x, y, 1+z

C11–H11A· · · O11

0.99

2.58

3.146(4)

116

C12–H12· · · O9

1.00

2.51

3.278(5)

133

1-x, -y, -z

C16–H16B· · · O7

0.98

2.50

3.409(4)

154

2-x, -y, 1-z

C16–H16B· · · O9

0.98

2.59

3.462(4)

148

2-x, -y, 1-z

C20–H20· · · O7

0.95

2.45

3.271(4)

145

2-x,1-y, -z

C23–H23· · · O4

0.95

2.51

3.441(3)

167

1+x, y, 1+z

327

planar distance of ca. 3.5 ˚ A. The distances between some of atoms C6-C22,

328

C7-C23 and C7-C22 are 3.421, 3.574 and 3.641 ˚ A, respectively, which are

329

typical of π–π contacts. The list of H-bonds are given in Table 8.

26

π−π

N−H···O

N−H···O

Figure 8: Crystal packing in [Cd2 (L4O)(NO3 )3 ]. Zigzag shaped chains in blue and orange which are running parallel to each other are constructed by N–H· · ·O H-bonds. π–π interactions connect two neighboring zigzag shaped chains.

27

330

4. Conclusions

331

There is no clear and simple trend that could be pointed out for metal

332

templated condensation reaction of dialdehyde and diamines and it is still a

333

largely empirical enterprise, but some insight into the nature of the reactions

334

has been gained by the isolation of complexes of non-macrocyclic ligands.

335

The isolation of [1+2]-condensation products might indicate that the course

336

of the reactions is strongly dependent on the nature of the templating metal

337

ion and the diamine i.e., the flexibility, spacer length, number and arrange-

338

ment of the donors used in the synthesis. Reaction of two ethylendiamine

339

and 1,2-diaminopropane with PL in the presence of Cd(II) ion yielded the

340

dinuclear complexes of [1+2]-nonmacrocyclic ligands derived from the con-

341

densation of one molecule of dialdehyde with two molecules of the diamine.

342

The same reaction with diethylentriamine and dipropylenetriamine, as the

343

triamines with two aliphatic spacers, however, yielded the [1+1]-macrocyclic

344

products. On the other hand, the same reaction with the tetramines with

345

three aliphatic spacer solely leads to the formation of the adduct of the amines

346

with Cd(II). Based on our previous work, the different binding properties of

347

Cd(II), Zn(II) and Ni(II) affect the type of species formed. Cd(II) similar

348

to Zn(II) promote the deprotonation of the hydroxyl group when compared

349

to Ni(II). Therefore, in complex formations of [Cd2 (L3O)(NO3 )3 (H2 O)], and

350

[Cd2 (L4O)(NO3 )3 ] spontaneous deprotonation of the alcohol moiety occurred

351

in the synthesis process.

28

352

5. Supplementary data

353

Crystallographic data for the structural analysis have been deposited with

354

Cambridge Crystallographic Data Centre, CCDC numbers 758169, 758170,

355

and 758171 for [Cd(L1OH)(NO3 )]NO3 , [Cd2 (L3O)(NO3 )3 H2 O], and [Cd2 (L4O)(NO3 )3 ]

356

respectively. These data can be obtained free of charge from The Cambridge

357

Crystallographic Data Centre.

358

6. Acknowledgements

359

360

This research was generously supported by grants from the Iran’s National Elite Foundation and University of Tabriz.

361

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362

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31