Arylazoimidazoliumchloride and chlorometallates: Spectroscopic and structural characterization

Article abstract of DOI:10.1016/j.ica.2010.02.006

Protonation or dialkylation of 2-(arylazo)imidazoles (RaaiH) has generated azoimidazolium motif (RaaiH₂⁺, RaaiR ^′H⁺, RaaiR^′₂⁺ where R = H, CH₃ and R^′ = Me,

Full text of DOI:10.1016/j.ica.2010.02.006

Inorganica Chimica Acta 363 (2010) 2080–2088
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Arylazoimidazoliumchloride and chlorometallates: Spectroscopic
and structural characterization
S. Halder a, G. Saha a, B.G. Chand a, A.D. Jana b, G. Mostafa b, J. Cheng c, T.-H. Lu c, C. Sinha a,
*
a Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata, West Bengal 700032, India
b Department of Physics, Jadavpur University, Kolkata, West Bengal 700032, India
c Department of Physics, National Tsing Hua University, Hsinchu 300, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 May 2009
Received in revised form 2 February 2010
Accepted 5 February 2010
Available online 12 February 2010
Protonation or dialkylation of 2-(arylazo)imidazoles (RaaiH) has generated azoimidazolium motif
0
0
+
(RaaiH2+, RaaiR H+, RaaiR 2 where R = H, CH3 and R0 = Me, Et, –CH2Ph). Electrostatic attraction between
imdazolium cation and counter ions like Clꢀ, ZnCl42ꢀ, PtCl6 has generated hydrogen bonded azoimi-
2ꢀ
dazolium-chloride/chlorometallated networks. The single crystal X-ray structure of 1-benzyl-2-(pheny-
lazo)imidazolium chloride shows tape like 1-D network of [Cl(H2O)4]ꢀ. Aquated Clꢀ forms 10
membered supracycle through hydrogen bonding with imidazolium ion. The X-ray structures of
Keywords:
+
[HaaiMe2 (1,3)]+[Me2NH2]+ [ZnCl4]2ꢀ and [MeaaiH2 ꢁH2O]2[PtCl6]2ꢀ show hydrogen bonded chlorometal-
Aryl-azo-imidazolium chloride
Chlorometallated azoimidazolium
X-ray structures
Tapelike aquated-chloride
Ladder
late chain penetrated into the channel developed by organic motif. Azoimidazolium units are associated
through
p
ꢁꢁꢁ
p
and C–Hꢁꢁꢁ
p
interactions to strengthen the supramolecular geometry.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
2. Experimental
Anion receptors are of considerable current interest in molecu-
lar recognition study [1–4]. Electrostatic interaction, hydrogen
2.1. Materials
bonding, D–HꢁꢁꢁA (D = donor, A = acceptor), D–Hꢁꢁꢁ
p
, and
p
ꢁꢁꢁ
p
inter-
ZnCl2, H2PtCl6 were purchased from Aldrich–Sigma. 1-alkyl-2-
(arylazo)imidazoles were synthesized by reported procedure
[14]. All other chemicals and solvents were reagent grade as
received.
actions have been exploited to recognize the anions. Protonated
amines or quaternary ammonium ions present in a ligand topology
make attractive receptors for anions [1,4–9]. Azole based H-recep-
tors (containing N–H unit as hydrogen donor) are effective binding
agents [10–12]. Presence of electron withdrawing substituents on
the aromatic part has significantly improved the stability of anion
binding [13]. We are engaged for last several years in the design of
azo functionalized imidazole molecules [14,15] and have been
used to study the anion binding property [16,17]. Halides (Xꢀ),
bihalides (HX2ꢀ), pseudohalides have been encapsulated in differ-
ent cavities in view of their participation in important chemical
and biological processes [3,4,18]. In this work we have used azoim-
idazolium ion to bind Clꢀ and chlorometallates, like tetrahedral
[ZnCl4]2ꢀ and octahedral [PtCl6]2ꢀ to prepare ionic solids. Crystal
structures of the compounds reveal that the hydrogen bonds,
2.2. Physical measurements
Microanalytical data (C, H, N) were collected on Perkin–Elmer
2400 CHNS/O elemental analyzer. Spectroscopic data were ob-
tained using the following instruments: UV–Vis spectra from Per-
kin–Elmer Lambda 25 spectrophotometer; IR spectra (KBr disk,
4000–450 cmꢀ1) from Perkin–Elmer RX-1 FTIR spectrophotometer
and 1H NMR spectra from Bruker (AC) 300 MHz FTNMR spectrom-
eter. Molar conductance was measured using Systronics-304 con-
ductivity meter.
C–Hꢁꢁꢁ
p
and
pꢁꢁꢁp interaction present to constitute supramolecular
2.3. Preparation of compounds
geometry.
2.3.1. Preparation of 1-methyl-2-(phenylazo)imidazolium chloride
(HaaiMeH+Clꢀ)(2a)
To methanolic solution (10 ml) of 1-methyl-2-(phenylazo)imid-
azole (0.2 g, 1.08 mmol), HCl solution (6 N) (1 ml) was added and
left for several days to evaporate. Orange crystalline compound
* Corresponding author. Tel.: +91 033 2414 6666x2458(O); fax: +91 033 2414
6584.
E-mail address: c_r_sinha@yahoo.com (C. Sinha).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.02.006

S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
2081
was separated, then filtered and washed with cold water. Residue
was redissolved in minimum volume of warm water and slowly
evaporated. Orange needle shaped crystals were isolated by filtra-
tion. Yield: 0.16 g (67%). The reactions are summarized in
Scheme 1.
red for 30 min. Methylchloride (0.15 g, 3.0 mmol) was added in
dropwise for 10 min. and refluxed for additional 2 h then cooled
and filtered. Filtrate was evaporated in vacuum. Dry residue was
extracted with CHCl3 and was filtered. The orange residue was dis-
solved in minimum volume warm water and filtered. Filtrate was
evaporated slowly and crystalline products were collected. Yield.
0.21 g (76%).
All other compounds were prepared by identical procedure in
the yield of 65–80%. Microanalytical data are: [HaaiH2+]Clꢀ (1a),
Anal. Calc. for C9H9N4Cl: C, 51.80; H, 4.32; N, 26.86. Found: C,
All other compounds were prepared by identical procedure in
the yield of 70-80%.
51.68; H, 4.27; N, 26.58%; UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 380 (2.13), 273 (8.15). [MeaaiH2+]Clꢀ (1b), Anal.Calc.
Microanalytical data are: [HaaiMe2+]Clꢀ (5a), Anal. Calc. for
C11H13N4Cl: C, 55.81; H, 5.50; N, 23.68. Found: C, 55.72; H, 5.42;
for C10H11N4Cl: C, 53.93; H, 4.94; N, 25.17. Found: C, 53.80; H, 4.88;
N, 25.24%; UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 376
N, 23.58%; UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1):
(3.45), 280 (9.05). [HaaiMeH+]Clꢀ (2a), Anal.Calc. for C10H11N4Cl:
375(4.40), 275(6.15). [MeaaiMe2+]Clꢀ (5b), Anal. Calc. for
C, 53.93; H, 4.94; N, 25.17. Found: C, 53.85; H, 4.91 N, 25.28%;
C12H15N4Cl: C, 57.49; H, 5.99; N, 22.36%. Found: C, 57.55; H,
UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 382 (3.10),
6.05; N, 22.24%; UV–Vis (methanol), kmax(e
x 10ꢀ4, molꢀ1 cmꢀ1):
270(7.89). [MeaaiMeH+]Clꢀ (2b), Anal. Calc. for C11H13N4Cl: C,
383 (2.30), 270(8.23). [HaaiEt2+]Clꢀ (6a), Anal. Calc. for C13H17N4Cl:
C, 58.98; H, 6.43; N, 21.17. Found: C, 59.06; H, 6.48; N, 21.25%.
[MeaaiEt2+]Clꢀ (6b), Anal. Calc. for C14H19N4Cl: C, 60.32; H, 6.82;
N, 20.11. Found: C, 60.40; H, 6.85; N, 20.24%; UV–Vis (methanol),
55.81; H, 5.50; N, 23.68. Found: C, 55.85; H, 5.44; N, 23.61%; UV–
Vis (methanol), kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 380 (2.30), 270
(8.00). [HaaiEtH+]Clꢀ (3a), Anal. Calc. for C11H13N4Cl: C, 55.81; H,
5.50; N, 23.68. Found: C, 55.74; H, 5.45; N, 23.60%; UV–Vis (meth-
kmax(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1):
382
(3.10),
270
(7.10).
anol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 381 (3.54), 270 (7.54).. [Meaai-
[Haai(CH2Ph)2+]Clꢀ (7a), Anal. Calc. for C23H21N4Cl: C, 71.04; H,
EtH+]Clꢀ (3b), Anal. Calc for C12H15N4Cl: C, 57.49; H, 5.99; N,
5.41; N, 14.41. Found: C, 71.10; H, 5.50; N, 14.35%; UV–Vis (meth-
22.36. Found: C, 57.55; H, 6.06; N, 22.26%; UV–Vis (methanol),
anol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 385 (4.25), 280 (8.140. Mea-
kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1):
383
(1.88);
277
(7.78)..
ai(CH2Ph)2+]Clꢀ (7b), Anal. Calc. for C24H23N4Cl: C, 71.55; H, 5.71;
[Haai(CH2Ph)H+]Clꢀ (4a), Anal. Calc. for C16H15N4Cl: C, 64.32; H,
N, 13.91. Found: C, 71.60; H, 5.75; N, 14.00%; UV–Vis (methanol),
5.03; N, 18.76. Found: C, 64.25; H, 5.00; N, 18.68%; UV–Vis (meth-
kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 390 (3.55), 280 (7.86).
anol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 390 (5.89), 283(8.55). [Mea-
.
ai(CH2Ph)H+]Clꢀ (4b), Anal. Calc. for C17H17N4Cl: C, 65.28; H,
5.44; N, 17.92. Found: C, 65.34; H, 5.50; N, 18.00%; UV–Vis (meth-
2.4. Preparation of azoimidazolium chlorometallates
anol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 386 (4.54), 278 (8.45).
2.4.1. [HaaiH2+]2ZnCl4 (8a)
2ꢀ
2.3.2. Preparation of 1,3-dimethyl-2-(phenylazo)imidazolium chloride
[HaaiMe2+] (Clꢀ)(5a)
To dry THF solution (20 ml) of 2-(phenylazo)imidazole (HaaiH)
(0.2 g, 1.16 mmol), NaH (50% paraffin) was added in pinch and stir-
An aqueous solution of ZnCl2 (30 mg, 0.122 mmol) in dilute HCl
(1:1, v/v) (5 ml) was added in dropwise to methanolic solution
(10 ml) of HaaiH (40 mg, 0.23 mmol). Orange solution was allowed
to evaporate slowly for a week at 15 °C. Crystals were deposited on
4
5
4
5
+
N
3
N
3
N
1
N
1
R/
H
Cl-
R
N
N
dil. HCl in MeOH
N
R
N
R
7
8
11
10
7
11
10
8
9
9
RaaiR/ H+Cl-
RaaiR/
, 1 -4
4
5
+
R/ = H (1)
N
3
Cl-
N
1
R/ = Me (2)
R/ = Et (3)
R
R
R/ = CH2Ph (4)
N
R'Cl, THF
N
R = R/ = Me (5)
R = R/ = Et (6)
7
8
11
10
R = R/ = CH2Ph (7)
9
R
RaaiR/2+Cl-, 5 - 7
Scheme 1. Synthesis of azoimidazolium chlorides (1–7).

2082
S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
the wall of beakers and collected by filtration and dried over CaCl2
in desiccator. Yield: 37 mg (54%).
anol), kmax
(e
ꢂ 10ꢀ4
,
]
moleꢀ1 cmꢀ1): 408 (2.00), 305 (7.89).
(16a): Anal. Calc. for C20H22N8Cl6Pt: C,
[HaaiHMe+]2[PtCl6
2ꢀ
All other compounds were prepared by identical procedure in
the yield of 50–70%.
30.69; H, 2.81; N, 14.32. Found: C, 30.61; H, 2.75; N, 14.25; UV–
Vis (methanol), kmax
(e
,
ꢂ 10ꢀ4 molꢀ1 cmꢀ1): 400 (1.90), 295
All other compounds were prepared by identical procedure in
(7.55). [MeaaiHMe+]2p[PtCl62ꢀ] (16b): Anal. Calc. for C22H26N8Cl6Pt:
the yield of 50–70%. Microanalytical data are: [HaaiH2+]2ZnCl4
C, 32.59; H, 3.21; N, 13.83Found: C, 32.64; H, 3.27; N, 13.75; UV–
2ꢀ
(8a): Anal. Calc. for C18H18N8Cl4Zn: C, 39.04; H, 3.25; N, 20.24.
Vis (methanol), kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 405 (2.05), 305
Found: C, 39.11; H, 3.27; N, 20.17%; UV–Vis (methanol),
(8.00). [HaaiHEt+]2[PtCl62ꢀ] (17a): Anal. Calc. for C22H26N8Cl6Pt: C,
kmax(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 388 (2.08), 285(7.88). [Mea-
32.59; H, 3.21; N, 13.83. Found: C, 32.50; H, 3.25; N, 13.9; UV–
aiH2+]2[ZnCl42ꢀ] (8b): Anal. Calc. for C20H22N8Cl4Zn: C, 41.29; H,
Vis (methanol), kmax(
e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 400 (2.05), 305
3.78; N, 19.27. Found: C, 41.20; H, 3.70; N, 19.17%; UV–Vis (meth-
(9.06). [MeaaiHEt+]2[PtCl62ꢀ] (17b): Anal. Calc. for C24H30N8Cl6Pt:
anol),
kmax
(
e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1):
(9a): Anal. Calc. for C20H22N8Cl4Zn: C,
390(3.30),
280(6.89).
C, 34.36; H, 3.58; N, 13.36. Found: C, 34.40; H, 3.50; N, 13.40%;
[HaaiHMe+]2[ZnCl4
]
UV–Vis (methanol), kmax
(7.85). [HaaiH(CH2Ph)+]2[PtCl6
(
e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 400 (2.10); 310
2ꢀ
2ꢀ
41.29; H, 3.78; N, 19.27. Found: C, 41.35; H, 3.67; N, 19.30%; UV–
]
(18a): Anal. Calc. for
Vis (methanol), kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 385 (3.56), 278
C32H30N8Cl6Pt: C, 41.11; H, 3.21; N, 11.99. Found: C, 41.23; H,
(7.68). [MeaaiHMe+]2[ZnCl42ꢀ] (9b): Anal. Calc. for C22H26N8Cl4Zn:
3.15; N, 12.10%; UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1):
C, 43.33; H, 4.27; N, 18.38. Found: C, 43.21; H, 4.20; N, 18.30%;
405 (2.25); 300 (8.85). [MeaaiH(CH2Ph)+]2[PtCl62ꢀ] (18b): Anal.
UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 388 (1.86), 280
Calc. for C34H34N8Cl6Pt: C, 42.40; H, 3.53; N, 11.64. Found: C,
(5.68). [HaaiHEt+]2[ZnCl42ꢀ] (10a): Anal. Calc. for C22H26N8Cl4Zn:
42.34; H, 3.60; N, 11.67%; UV–Vis (methanol), kmax
(
e
ꢂ 10ꢀ4
,
C, 43.33; H, 4.27; N, 18.38. Found: C, 43.22; H, 4.33; N, 18.30%;
molꢀ1 cmꢀ1): 425 (1.85), 315(7.55). [HaaiMe2+]2[PtCl62ꢀ] (19a):
Anal. Calc. for C22H26N8Cl6Pt: C, 32.59; H, 3.21; N, 13.83. Found:
UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 390 (2.05), 280
(7.68). [MeaaiHEt+]2[ZnCl42ꢀ] (10b): Anal. Calc. for C24H30N8Cl4Zn:
C, 32.66; H, 3.28; N, 13.92%; UV–Vis (methanol), kmax
(
e
ꢂ 10ꢀ4
,
C, 45.19; H, 4.71; N, 17.57. Found: C, 45.26; H, 4.63; N, 15.67%; UV–
molꢀ1 cmꢀ1): 390 (2.20), 300 (8.85). [MeaaiMe2+]2[PtCl62ꢀ] (19b):
Anal. Calc. for C24H30N8Cl6Pt: C, 34.36; H, 3.58; N, 13.36. Found:
Vis (methanol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 388 (3.10), 275 (7.55).
[HaaiH(CH2Ph)+]2[ZnCl42ꢀ] (11a): Anal. Calc. for C32H30N8Cl4Zn: C,
C, 34.42; H, 3.63; N, 13.32%; UV–Vis (methanol), kmax
(
e
ꢂ 10ꢀ4
,
52.36; H, 4.09; N, 15.27. Found: C, 52.30; H, 4.03; N, 15.30%; UV–
molꢀ1 cmꢀ1): 410 (2.25), 301 (7.90). [HaaiEt2+]2[PtCl62ꢀ] (20a):
Anal. Calc. for C22H26N8Cl6Pt: C, 36.02; H, 3.93; N, 12.93. Found:
Vis (methanol), kmax
(e
x 10ꢀ4
,
molꢀ1 cmꢀ1): 400 (2.00), 305
(8.50). [MeaaiH(CH2Ph)+]2[ZnCl4
]
(11b): Anal. Calc. for
C, 36.06; H, 3.88; N, 12.90; UV–Vis (methanol), kmax(
e
ꢂ 10ꢀ4
,
2ꢀ
C34H34N8Cl4Zn: C, 53.59; H, 4.47; N, 14.71. Found: C, 45.26; H,
molꢀ1 cmꢀ1): 400 (1.45), 305 (8.00). [MeaaiEt2+]2[PtCl62ꢀ](20b):
Anal. Calc. for C28H38N8Cl6Pt: C, 37.58; H, 4.21; N, 12.53 Found:
4.63; N, 15.67%; UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4, moleꢀ1 cmꢀ1):
395 (1.86), 280 (8.35). [HaaiMe2+]2[ZnCl42ꢀ] (12a): Anal. Calc. for
C, 37.66; H, 4.28; N, 12.47%; UV–Vis (methanol), kmax
(
e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 405 (2.10), 305 (8.45). [Haai(CH2Ph)2+][PtCl6
]
2ꢀ
C22H26N8Cl4Zn: C, 43.32; H, 4.27; N, 18.38. Found: C, 43.30; H,
4.37; N, 18.24%; UV–Vis (methanol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1):
(21a): Anal. Calc. for C46H42N8Cl6Pt: C, 49.55; H, 3.77; N, 10.05.
395 (2.25), 290 (7.78). [MeaaiMe2+]2[ZnCl42ꢀ] (12b): Anal. Calc.
Found: C, 49.45; H, 3.71; N, 10.00%; UV–Vis (methanol),
for C24H30N8Cl4Zn: C, 45.18; H, 4.71; N, 17.57. Found: C, 45.22;
kmax
(e
ꢂ 10ꢀ4
,
molꢀ1cmꢀ1): 410 (2.30), 310 (8.50). [Mea-
ꢂ 10ꢀ4
,
ai(CH2Ph)2+][PtCl6
]
(21b): Anal. Calc. for C48H46N8Cl6Pt: C,
2ꢀ
H, 4.67; N, 17.50%; UV–Vis (methanol), kmax
(
e
molꢀ1 cmꢀ1): 397 (1.89); 280 (7.68). [HaaiEt2+]2[ZnCl42ꢀ] (13a):
Anal.Calc. for C26H34N8Cl4Zn: C, 46.90; H, 5.11; N, 16.83. Found:
50.43; H, 4.03; N, 9.81. Found: C, 50.50; H, 4.04; N, 10.00%; UV–
Vis (methanol), kmax
(e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 410 (2.15), 310 (7.85).
C, 46.95; H, 5.07; N, 16.74%; UV–Vis (methanol), kmax
(
e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 400 (2.02), 295 (7.68). [MeaaiEt2+]2[ZnCl42ꢀ] (13b):
Anal.Calc. for C28H38N8Cl4Zn: C, 48.46; H, 5.48; N, 16.15. Found:
2.5. X-ray diffraction study
C, 48.38; H, 5.39; N, 16.24%; UV–Vis (methanol), kmax
(
e
ꢂ 10ꢀ4
,
]
The crystallographic data are shown in Table 1. Single crystals
+
molꢀ1 cmꢀ1): 397 (1.89), 280 (8.00). [Haai(CH2Ph)2[ZnCl4
of [Haai(CH2Ph)H+](Clꢀ) 2H2O (4a) and [MeaaiH2 ꢁH2O]2 [PtCl6
]
2ꢀ
2ꢀ
(14a): Anal. Calc. for C46H42N8Cl4Zn: C, 60.43; H, 4.60; N, 12.26.
(15b) were grown by evaporation of aqueous solution where as
Found: C, 60.45; H, 4.67; N, 12.37%; UV–Vis (methanol),
few drops of DMF added to methanolic solution of [HaaiMe2
kmax
(e
ꢂ 10ꢀ4
,
molꢀ1 cmꢀ1): 402 (2.05), 300 (7.85). [Mea-
(1,3)]+ [ZnCl4]2ꢀ (12a) and evaporated to isolate crystals of
2
ai(CH2Ph)2+][ZnCl4
]
(14b): Anal. Calc. for C48H46N8Cl4Zn: C,
[HaaiMe2 (1,3)]+[Me2NH2]+ [ZnCl4]2ꢀ. DMF undergoes hydrolysis
to generate dimethylamine which upon protonation may form
Me2NH2+. Suitable single crystals of 4a (0.3 ꢂ 0.3 ꢂ 0.25 mm3),
12a (0.2 ꢂ 0.2 ꢂ 0.1 mm3) and 15b (0.17 ꢂ 0.13 ꢂ 0.05 mm3) were
mounted on a Brucker CCD area detector equipped with fine fo-
2ꢀ
61.19; H, 4.89; N, 11.90. Found: C, 61.25; H, 4.94; N, 12.00%; UV–
Vis (methanol), kmax
(
e
ꢂ 10ꢀ4, molꢀ1 cmꢀ1): 408 (2.43), 290 (9.58).
2.4.2. [HaaiH2+]2[PtCl62ꢀ] (15a)
An aqueous solution of K2PtCl6 (60 mg, 0.123 mmol) in dilute
HCl (1:1, v/v) (5 ml) was added in dropwise to methanolic solution
(10 ml) of HaaiH (45 mg, 0.26 mmol). Orange-red solution was al-
lowed to evaporate slowly for a week at 150 °C. Crystals were
deposited on the wall of beakers and collected by filtration and
dried over CaCl2 in desiccator. Yield: 46 mg (53%). All other com-
pounds were prepared by identical procedure in the yield of 50–
70%.
cused sealed tube graphite monochromated Mo Ka (k = 0.71073 Å)
radiation. The unit cell parameters and crystal-orientation matri-
ces were determined for these compounds by least squares
refinements of all reflections. The intensity data were corrected
for Lorentz and polarization effects and an empirical absorption
correction were also employed using the SAINT program. All these
structures were solved by direct methods and followed by succes-
sive Fourier and difference Fourier syntheses. Full matrix least
squares refinements on F2 were carried out using SHELXL-97 with
anisotropic displacement parameters for all non-hydrogen atoms.
Hydrogen atoms were constrained to ride on the respective carbon
or nitrogen atoms with anisotropic displacement parameters
equal to 1.2 times the equivalent isotropic displacement of their
parent atom in all cases. Complex neutral atom scattering fac-
tors were used throughout the experiments. All calculations were
All other compounds were prepared by identical procedure in
the yield of 50–70%. Microanalytical data are: [HaaiH2+]2[PtCl6
]
2ꢀ
(15a): Anal. Calc. for C18H18N8Cl6Pt: C, 28.64; H, 2.39; N, 14.85.
Found: C, 28.51; H, 2.33; N, 14.94%; UV–Vis (methanol),
kmax(e
ꢂ 10ꢀ4
,
moleꢀ1 cmꢀ1): 410 (1.68), 305 (7.85). [Mea-
aiH2+]2[PtCl62ꢀ] (15b): Anal. Calc. for C20H22N8Cl6Pt: C, 25.12; H,
2.30; N, 11.72. Found: C, 25.00; H, 2.33; N, 11.90%; UV–Vis (meth-

S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
2083
Table 1
Summarized crystallographic data for 4a, 12a and 15b.
[HaaiBzH+](Clꢀ). 2H2O (4a)
[HaaiMe2 (1,3)]+ [Me2NH2]+ [ZnCl4]2ꢀ (12a)
[MeaaiH2+.H2O]2 [PtCl6]2ꢀ (13b)
Empirical formula
Formula weight
T (K)
C16H19ClN4O2
334.80
295(2)
C13H21Cl4N5Zn
454.52
294(2)
C20H26Cl8N8O2Pt
818.28
298(2)
Crystal system
Space group
Crystal size (mm)3
a (Å)
orthorhombic
P212121
monoclinic
P21/c
triclinic
P1
ꢀ
6.2183(6)
12.4867(11)
22.158(2)
90.00
90.00
90.00
1720.5(3)
4
7.4248(5)
15.5073(11)
17.7261(12)
90.00
90.5130(10)
90.00
2040.9(2)
4
7.7841(5)
10.4269(7)
18.2641(12)
88.5880(10)
85.8470(10)
81.0220(10
1460.25(17)
2
b (Å)ab
cl
h
c (Å)
a
(°)
b (°)
c
(°)
V (Å)3
Z
l
(Mo K
h range
hkl range
Dcalc (mg mꢀ3
a
) (mmꢀ1
)
0.237
1.84 < h < 28.33
1.731
1.74–28.30
5.388
1.12–28.29
ꢀ7 6 h 6 8, ꢀ16 6 k 6 16, ꢀ29 6 l 6 23
ꢀ9 < h < 8; ꢀ20 < k < 15;ꢀ23 < l < 23
ꢀ10 < h < 10; ꢀ13 < k < 13;ꢀ24 < l < 23
)
1.293
704
1.479
208
1.861
350
Refine parameters
Total reflections
11 003
4 139
0.0424
0.1108
0.895
12 775
4 862
0.0553
0.1112
0.892
14 632
6 681
0.0425
0.1243
1.002
Unique reflections
a
R1 [I > 2
r
(I)]
b
wR2
Goodness-of-fit (GOF) on F2
a
R =
R
||Fo|ꢀ|Fc||/
R|Fo|.
b
wR2 = [R R r r
w(Fo2-Fc2)2/ w(Fo2)2]1/2, w = 1/[r2 (Fo2) + (0.0695P)2 + 0.0000P] for 4a; w = 1/[ 2(F0)2 + (0.0470P)2 + (2.7391P)] for 12a; w = 1/[ 2(F0)2 + (0.0713P)2+ (0.0000P)]
for 13b where P = ((F02 + 2Fc2)/3.
carried out using SHELXS 97 [19], SHELXL97 [20], ORTEP-3 [21], and PLA-
TON 99 [22] program.
groups. This supports that both ground and excited states are influ-
enced by substituents.
The 1H NMR spectra of the compounds 1–7 are taken in CD3CN.
The atom numbering pattern is shown in Scheme 1 and data are gi-
ven in Supplementary material (Table S1). The proton signals are
assigned on comparing with the spectra of RaaiR0 [14,15], spin-spin
interaction and effect of substitution. Imidazole protons (4-, 5-H)
appear as broad single resonance at 7.0–7.2 ppm. The broadening
may be due to rapid proton exchange between two positions.
The aryl protons (7-H to 11-H) are shifted to upfield side due to
+I effect of 9-Me substituent in p-tolylazoimidazole molecules
(b). 1-alkyl-2-(arylazo)imidazolium chloride (1–4) show proton
resonance for R0: 1-Me as a sharp singlet at 4.33 ppm; 1-Et exhibits
3. Results and discussion
3.1. Azoimidazolium chloride
1-Alkyl-2-(arylazo)imidazoles (RaaiR0) are gummy mass [14,15]
while addition of HCl has isoꢀlated crystalline water soluble ionic
+
(1:1 conducting) [RaaiHR0 ]Cl (1–4) compounds (Scheme 1). 1,3-
Di-alkyl-2-(arylazo)imidazolium chloride ([RaaiR02+]Clꢀ (5–7) are
prepared by alkylation of RaaiH with large excess of alkyl chloride.
They are also crystalline and water soluble ionic compounds. Sin-
gle crystal X-ray diffraction study of a representative compound,
1-benzyl-2-(phenylazo)imidazolium chloride, has confirmed the
structure of the molecule.
1-(CH2)- as quartet at a
triplet splitting pattern at a
v
. 4.80 ppm (J = 9.0 Hz) and methyl (-Me) as
v
. 1.50 ppm (J = 10.0 Hz); 1-CH2–(Ph)
shows sharp singlet at 5.18 ppm 1,3-dialkyl-2-(arylazo)imidazoli-
um chloride show a single resonance for R0 and R00: 1,3-Me2 of 6
show a sharp singlet at 4.25 ppm; 1,3-Et2 of [RaaiEt2+](Clꢀ) (7) ex-
The IR spectra of the compounds show broad, medium intense
band centerd at 3420 cmꢀ1 which is referred to (H2O) and a med-
ium intense band observed at 1620–1640 cmꢀ1 which may be as-
signed to bending mode of water cluster [23]. Upon heating in
the temperature range 90–110 °C the crystallized water was re-
moved and IR spectra do not further show corresponding vibration
even on exposure to air for 24 h. The –N@N- and –C@N- appear at
1400–1420 and 1600–1630 cmꢀ1, respectively.
hibit 1-(CH2)- as quartet at a
v
. 4.85 ppm and methyl (-Me) as trip-
let splitting pattern at av. 1.5 ppm; 1-CH2–(Ph) of 8 appears at
5.10 ppm.
3.2. Molecular structure of [Haai(CH2Ph)H+](Clꢀ), 2H2O (4a)
The absorption spectrum of RaꢀaiR0 and protonated form,
[RaaiR0H]+Clꢀ (1–4) and [RaaiR0R00]+Cl (5-7) in methanol solution
show absorption band around 270–400 nm with a molar absorp-
tion coefficient in the order of 104 Mꢀ1 cmꢀ1 and a tail extending
into 500 nm. From the analogy with the absorption spectrum of
The molecular structure of [HaaiCH2PhH+](Cl-), 2H2O (4a) is
shown in Fig. 1a and bond parameters are listed in Table 2.
The azophenyl and imidazole rings are virtually coplanar as indi-
cated by the torsion angle, C(1)–N(1)–N(2)–C(7), 178.91(17)° and
the dihedral of two planes is 9.20(12)°. Maximum deviation of
N(2) from mean plane formed by phenyl, azo and imidazole
groups is 0.050(2) Å. Nonplanarity of benzylic phenyl group
(C(11)–C(16)) with imidazole ring is due to –CH2- group. The loss
of planarity may be due to the result of 1-CH2Ph group in the
imidazole ring. The N(1)–N(2) bond length is 1.258(3) Å which
is comparable to the reported data [25–27] 1.252(2) Å for 1-
methyl-2-(phenylazo)imidazolium perchlorate. The N@N bond
length is shorter than that of the reported distance (1.267(3) Å)
azobenzene [24], it is likely that the large absorption band around
*
270–330 nm corresponds to
400 nm corresponds to n–
p–p
transitions, while the tail 370–
*
*
p transition. However, the p–p band
exhibits bathochromic shifts by ꢃ30 nm compared with azoben-
*
zene, while the n–
p
band shows little shift. As a consequence,
*
*
the energy separation between the
p
–p
and n–
p
transitions in
arylazoimidazoles is narrower than that for azobenzene. The band
is significantly influenced by substitutents at aryl and imidazolyl

2084
S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
Fig. 1. (a) The molecular structure of [HaaiCH2PhH+]Clꢀ, 2H2O with atom numbering scheme, (b) water–chloride pentameric tape constituted by [Cl(H2O)4]ꢀ unit.
[O(2)–H(2A)ꢁꢁꢁO(1): O(2)–H(2A), 0.78(3) Å; H(2A)ꢁꢁꢁO(1), 2.01(3) Å;
Table 2
Selected bond length (Å) and bond angles (°) of [HaaiCH2PhH+]Clꢀ, 2H2O (4a).
O(2)ꢁꢁꢁO(1), 2.780(3) Å;O(2)–H(2A)ꢁꢁꢁO(1), 175(3)° and symmetry:
1 ꢀ x, 1/2 + y, 1/2 ꢀ z. O(1)–H(1B)ꢁꢁꢁO(2): O(1)–H(1B), 0.77(4) Å;
H(1B)—O(2), 1.94(4) Å; O(1)ꢁꢁꢁO(2), 2.708(3) Å; O(1)–H(1B)ꢁꢁꢁO(2),
171(3)° and symmetry: 1/2 ꢀ x, ꢀy,1/2 + z; O(2)–H(2B)ꢁꢁꢁCl:
O(2)–H(2B), 0.73(3) Å; H(2B)ꢁꢁꢁCl, 2.42(3) Å; O(2)—Cl, 3.122(2) Å;
O(2)–H(2B)ꢁꢁꢁCl, 164(3)° and symmetry: x, y, z. O(1)–H(1A)ꢁꢁꢁCl:
O(1)–H(1A), 0.88(3) Å; H(1A)ꢁꢁꢁCl, 2.22(3) Å; O(1)ꢁꢁꢁCl, 3.091(3)
Å;O(1)–H(1A)ꢁꢁꢁCl, 169(3)° and symmetry: ꢀx, ꢀ1/2 + y,1/2 ꢀ z.
C(3)–H(3)ꢁꢁꢁCg(3): C(3)–H(3), 0.96(3) Å; H(3)ꢁꢁꢁCg(3), 3.09(2) Å;
C(3)ꢁꢁꢁCg(3), 3.758(3) Å; C(3)–H(3)ꢁꢁꢁCg(3), 130.0(6)° and symme-
try: ꢀ1 + x, y, z]. The cyclic chloride-water pentamer is almost pla-
nar with maximum deviation for oxygen atom ranging upto 0.22 Å
from the mean plane from which the Clꢀ anion deviates only by
0.01 Å. The angle between successive mean planes of adjacent
fused rings is 40.91° rendering the water tape a slight zigzag
topography. This value is little larger than that observed in the
pure water pentameric tape [56] which is 28.7°. The tape is con-
Bond length (Å)
Bond angle (°)
N(1)–N(2)
N(1)–C(1)
N(2)–C(7)
1.2574(25)
1.4156(27)
1.3964(26)
N(2)–N(1)–C(1)
N(1)–N(2)–C(7)
C(7)–N(3)–C(8)
115.35(18)
110.76(17)
108.95(17)
for 1-ethyl-2-(naphthyl-azo)imidazolium hexafluorophosphate [27].
The steric crowding and better electron donating ability of naph-
thyl group may be reason for the elongation. The N(azo)–C(imid-
azole), N(2)–C(7), 1.393(3) Å, is shorter than N(azo)–C(phenyl),
N(1)–C(1), 1.418(3) Å which indicates a stronger intramolecular
interaction between azo and imidazole group.
The imidazolium ion is formed by protonation of N(3) center of
imidazole. Presence of Clꢀ balances charge of the species. H2O mol-
ecules are hydrogen bonded with Clꢀ and constitute an aquated
charged species [Cl(H2O)4]ꢀ (Fig. 1b). Water, the most important
molecule for life, due to its hydrogen bonding ability in various
cooperative modes can form water oligomers and polymers having
various shapes and topology [28–56]. Reports of polymeric water
association are relatively recent, only chain, tape and layer type
geometries have been observed [53–56]. Water pentamer which
generally has been observed to have fused tape like structure in
the crystalline host [56] is the dominant constituent of liquid water
at 298 K. Anomalous thermodynamic properties of liquid water has
been proposed to be the result of fluctuation of number of penta-
mers at that temperature. Water anion associations are gaining
prominence recently [57,58] due to their importance in solvation
phenomena and biological ion-transport. Pentameric water tape
involving Clꢀ anion was evident in literarure [59,60] in which
two chloride anion replaced two water molecules in the pentamer-
ic ring constituting the tape. Herein we also find a novel pentamer-
ic water chloride ring involving only one chloride anion which
extends into a tape by the process of fusion of successive penta-
meric rings through a common edge (Fig. 1b). The anionic chain
is further hydrogen bonded to arylazoimidazolium ion. Two sides
of the supracycle are attached to the protonated imidazole via
hydrogen bonding imidazole-N+–HꢁꢁꢁO(H2). Pendant phenyl ring
nected to the organic
p–p stacked planes on both the edges
through the weak –C–HꢁꢁꢁCl hydrogen binding. The ribbon extends
along the crystallographic [1 0 0] direction through a rectangular
channel space in between two
p–p stacked planes (Fig. 2). The
water–chloride pentamer (H2O)4Clꢀ constituting the zigzag tape
(Fig. 1b) is almost planar which is self-assembled and stabilized
by hydrogen bonding interaction within itself. Only a weak C–
HꢁꢁꢁClꢀ bond establishes its contact with the organic layer. The
ubiquity of Clꢀ and water in biological systems leads us to believe
that the water–chloride association of the type presented here may
aid in the deeper understanding of Clꢀ and proton transport in bio-
logical systems as well in the solvation phenomena of chloride
salts in water.
3.3. Azoimidazolium chlorometallates
Chlorometallates of Zn(II) and Pt(IV) have been used to syn-
thesise azoimidazolium salts in dilute HCl medium (Eqs. 1 and
2).The mixture of acidic solution (HCl) of ZnCl2 or H2[PtCl6]
and arylazoimidazolium chloride in aqueous solution has sepa-
rated orange crystalline compounds on slow evaporation in air
for a week. The composition of the compounds are established
by microanalytical data, molar conductance and spectroscopic
(FTIR, NMR (Supplementary material (Table S1)) data. The com-
and 1-benzyl group undergo
p
ꢁꢁꢁ
p interaction with neighboring
partners resulting a -sheet. Water-chloride tapes take position in-
p
side the rectangular channel space between two layers and devel-
op a chloride sponge (Fig. 2). Hydrogen bonds are closer to linear
geometry with D–HꢁꢁꢁA angle within 164–175°. OꢁꢁꢁO distances
are 2.70 Å and 2.78 Å and O—Cl distances are 3.09 Å and 3.12 Å
+
þ
pounds are abbreviated [RaaiR0H ]2[ZnCl42ꢀ] (8–11), [RaaiR02
]
]
2
[ZnCl42ꢀ](12–14), [RaaiR0H+]2[PtCl6
[PtCl62ꢀ](19–21).
]
(15–18) and [RaaiR02
2ꢀ
þ
2

S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
2085
HCl=MeOH—H2
O
þ
ZnCl2 þ 2RaaiR0 or ½RaaiR0 ꢄClꢀ
!
½RaaiR0Hþꢄ2½ZnCl42ꢀꢄ or ½RaaiR20 þꢄ2½ZnCl42ꢀÞꢄ
ð1Þ
ð2Þ
2
8—11
12—14
HCl=MEOHH2
O
þ
H2½PtCl6ꢄ þ 2RaaiR0 or ½RaaiR0 ꢄClꢀ
!
½RaaiR0Hþꢄ2½PtCl62ꢀꢄ or ½RaaiR20 þꢄ2½PtCl62ꢀÞꢄ
2
15—18
19—21
3.4. Spectral studies
torted tetrahedral geometry which is measured from the magni-
tude of bond lengths and bond angles (Table 3). The Zn–Cl
distances lie in between 2.26 to 2.29 Å. The Cl–Zn–Cl bond angles
107–113° are description of tetrahedral angular data. The struc-
tural distortion is inconsistent with the electronic configuration
of Zn(II) (d10), however, it could be assessed from hydrogen bond-
ing and noncovalent interaction present in the supramolecule (vide
infra). Dimethylammonium ion in the structure may be coming
from the metal assisted hydrolysis of DMF [65] in the acidified
IR bands were assigned on comparing with free ligand data
[14,15]. Moderately intense stretching at 1595–1600 and 1435–
1445 cmꢀ1 are due to
m(C@N) and m(N@N), respectively for both
types of complexes. The ionic solids, [RaaiR0H+]2[MCln]ꢀ are soluble
in acetonitrile and the solution electronic spectra were recorded in
the wavelength range 250–900 nm. There are two bands corre-
sponding to (
e
ꢃ104 molꢀ1 dm3 cmꢀ1) 280–310 and 375–420 nm
and the bands show bathochromic shifting by 10–30 nm compared
to the precursor arylazoimidazolium chloride (1–7). On comparing
with free ligand spectra [61–64], and as per discussion in previous
section we may conclude that these bands are due to intramolecu-
lar charge transfer transitions.
medium. ZnCl42ꢀconstitutes a 1-D chain via hydrogen bonding
+
with Me2NH2
.
ZnCl42-
HCl
H
+
H3C
H3C
H3C
N
N
CHO
H2O
+ HCOO-
+
The 1H NMR spectra of the compounds are recorded in CD3CN.
The atoms numbering pattern are shown in Scheme 1. Data (Sup-
plementary material (Table S1)) reveal that the signals in the spec-
tra of the compounds are shifted to downfield side relative to free
ligand values and most significant downfield shifting is observed to
imidazole-protons. 4- and 5-H are shifted to higher d by 0.2–0.4
ppm relative to free ligand values. This supports the interaction
of metal ions with these protons. Imidazole protons appear at
7.2–7.4 ppm as broad singlet. Aryl signals shift as usual on Me-
substitution.
H
H3C
1,3-Dimethyl-2-(phenylazo)imidazolium ion is a constituent of
1-D chain by hydrogen bonding interaction with Cl of ZnCl24ꢀ: N–
HꢁꢁꢁCl(ZnCl3) (N(5)–H(5a)ꢁꢁꢁCl(3): N(5)ꢁꢁꢁCl(3), 3.204 Å; H(5a)ꢁꢁꢁCl(3),
2.330 Å;N(5)–H(5a)ꢁꢁꢁCl(3), 163.39° Symmetry, 1 ꢀ x, 1/2 + y, 1/
1 ꢀ 2 ꢀ z. N(5)– H(5b)ꢁꢁꢁCl(2): N(5)ꢁꢁꢁCl(2), 3.149 Å; H(5b)ꢁꢁꢁCl(2),
2.359 Å;N(5)–H(5b)ꢁꢁꢁCl(2), 146.45° Symmetry, ꢀx,1/2 + y, 1/
1 ꢀ 2 ꢀ z) and (imidazole)C–HꢁꢁꢁCl (C(9)–H(9)ꢁꢁꢁCl(3): C(9)–
H(9)ꢁꢁꢁCl(3): C(9)ꢁꢁꢁCl(3), 3.629 Å; H(9)ꢁꢁꢁCl(3), 2.784 Å; C(9)–
H(9)ꢁꢁꢁCl(3), 151.36° and symmetry, 1 ꢀ x,1 ꢀ y,1 ꢀ z). HaaiMe2
3.5. Structure description of chlorometallates [HaaiMe2
(1,3)]+[Me2NH2]+ [ZnCl4]2ꢀ (12a)
(1,3)]+ forms a separate
p
-chain in which the basis motif is a
pꢁꢁꢁp
The crystal structure consists of a discrete tetrahedral [ZnCl42ꢀ],
1,3-dimethyl-2-(phenylazo)imidazolium
interacted dimmer. Both imidazole and phenyl fragments are pla-
nar. Two groups around N@N are not perfectly planar and the dihe-
dral angle between the two least square planes is 3.4(2)°. The N@N
bond length is 1.243(4) Å. The distance is slightly shorter than
and
N,N-dimethyl
ammonium ions. Fig. 3 represents an ORTEP view of the compound
with the atom numbering scheme. The [ZnCl42ꢀ] assumes a dis-
Fig. 2. Water–chloride tapes inside the rectangular channel space between two layers.

2086
S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
Fig. 3. (a) ORTEP of [Pai-Me2 (1,3)+] [Me2NH2+] [ZnCl42ꢀ], (b) C–Hꢁꢁꢁ
p and pꢁꢁꢁp
stacked ladder of [HaaiMe2 (1,3)+] [Me2NH2+] [ZnCl42ꢀ].
tween C–H of imidazolyl-N-CH3 of [HaaiMe2 (1,3)]+ and
p-cloud
Table 3
Selected bond length (Å) and bond angles (°) of [Haai-Me2 (1,3)]+ [Me2NH2]+ [ZnCl4]2ꢀ
(12a).
of phenyl group (Hꢁꢁꢁ
p
, 4.191 Å, \C–Hꢁꢁꢁ
p, 3.36° and symmetry:
ꢀx, 1 ꢀ y, 1 ꢀ z) of neighboring [HaaiMe2 (1,3)]+ constitutes 1-D
Bond length (Å)
Bond angle (°)
chain (Fig. 3b). Inter-chain
pꢁꢁꢁp interaction between Cgs of imi-
dazolium ion and phenyl group of neighboring ion is Cg(Imidazoli-
um)ꢁꢁꢁCg(phenyl): distance = 4.433 Å, = 3.36° and symmetry:
1 ꢀ x, 1 ꢀ y,1 ꢀ z). These two interactions form 1-D -chain. The
chains are running in antiparallel fashion. This arrangement
interaction between the ring centroid
Zn–Cl(1)
Zn–Cl(2)
Zn–Cl(3)
Zn–Cl(4)
C(1)–N(3)
C(7)–N(1)
N(1)–N(3)
2.2944(10)
2.2576(11)
2.2818(10)
2.2671(11)
1.418(4)
Cl(2)–Zn–Cl(1)
Cl(3)–Zn–Cl(1)
Cl(4)–Zn–Cl(1)
Cl(2)–Zn–Cl(3)
Cl(2)–Zn–Cl(4)
Cl(4)–Zn–Cl(3)
N(3)–N(1)–C(7)
N(1)–N(3)–C(1)
107.11(4)
106.96(4)
113.10(4)
107.94(4)
113.32(5)
108.11(4)
113.8(3)
a
p
facilitates in a strong C–Hꢁꢁꢁ
p
1.391(4)
1.243(4)
(Cg) of phenyl ring and N-CH3 of [HaaiMe2 (1,3)]+) [(C(10)–
H(10b)ꢁꢁꢁCg(pheyl): H(10b)ꢁꢁꢁCg(phenyl), 2.816 Å; C(10)ꢁꢁꢁCg
(phenyl), 3.63 Å; C(10)–H(10b)ꢁꢁꢁCg(phenyl), 143.03° and symme-
try, 1 ꢀ x, 1 ꢀ y,1 - z) and an interaction between Cg(phenyl) and
Cg(imidazole) of adjacent molecules (Cg(phenyl)ꢁꢁꢁCg(imidazole):
113.8(3)
reported data of other azoimidazole compounds (1.258 (6) Å)
[7,8,17–19] and azoimidazolium ions (1.26(1) Å) [17–19]. The
bonding strength between azo-N(3) and phenyl-[C(1)–N(3),
1.418(4) Å] is weaker than that of azo-N(1) and imidazole-C(7)
[C(7)–N(1), 1.391(4) Å]. This suggests that the intramolecular
interaction between azo and imidazole functions is stronger than
4.191 and 4.433 Å). Every parallel
p-stacked cations are linked by
2ꢀ
two ZnCl4 ions on either side of the ladder through imidazolium
(C(9)–H(9)ꢁꢁꢁCl(3): C(9)–H(9)ꢁꢁꢁCl(3): C(9)ꢁꢁꢁCl(3), 3.629 Å; H(9)ꢁꢁꢁ
Cl(3), 2.784 Å;C(9)–H(9)ꢁꢁꢁCl(3), 151.36° and symmetry, 1 ꢀ x,
1 ꢀ y, 1 ꢀ z) which, in turn, result in a 3D supramolecular system
[66].
that of phenyl orbital. The presence of the C–Hꢁꢁꢁ
p interaction be-
Fig. 4. Molecular view of [MeaaiH2. H2O+]2 PtCl6
.
2ꢀ

S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
2087
3.6. [MeaaiH2+. H2O]2[PtCl6]2ꢀ (15b)
H(6)ꢁꢁꢁO(2): N(6)–H(6), 0.86; H(6)ꢁꢁꢁO(2), 1.850; N(6)ꢁꢁꢁO(2),
2.705(9) Å; 173.00°. N(5)–H(5a)ꢁꢁꢁCl(5):
\N(6)–H(6)ꢁꢁꢁO(2),
2ꢀ
The crystal structure consists of a discrete octahedral PtCl6
,
N(5)–H(5a), 0.86; H(5)ꢁꢁꢁCl(5), 2.480; N(5)ꢁꢁꢁCl(5), 3.252(6) Å;
\N(5)–H(5a)ꢁꢁꢁCl(5), 149.00°; symmetry, 2 ꢀ x, 1 - y, 1 ꢀ z. O(1)–
H(1)ꢁꢁꢁCl(1): O(1)–H(1), 0.85; H(1)ꢁꢁꢁCl(1), 2.67(2); O(1)ꢁꢁꢁCl(1),
3.462(6) Å; \O(1)–H(1)ꢁꢁꢁCl(1), 155.0°; symmetry, 1 ꢀ x,
2 ꢀ y,1 ꢀ z. O(1)–H(2)ꢁꢁꢁCl(4): O(1)–H(2), 0.85; H(2)ꢁꢁꢁCl(4), 2.770;
O(1)—Cl(4), 3.398(6) Å; \O(1)–H(2)ꢁꢁꢁCl(4), 132.0°; symmetry,
2 ꢀ x, 1 ꢀ y,1 ꢀ z. O(2)–H(2B)ꢁꢁꢁCl(3): O(2)–H(2B), 0.92(6);
H(2B)ꢁꢁꢁCl(3), 2.59(6); O(2)ꢁꢁꢁCl(3), 3.507(6) Å;\O(2)–H(2B)—Cl(3),
175(10)°; symmetry, 1 ꢀ x, 2 ꢀ y, 1 ꢀ z O(2)–H(2C)ꢁꢁꢁCl(4): O(2)–
H(2C), 0.92(7); H(2C)ꢁꢁꢁCl(4), 2.67(8); O(2)ꢁꢁꢁCl(4), 3.481(6) Å;
\O(2)–H(2C)ꢁꢁꢁCl(4), 148(6)°; symmetry, 2-x,2-y,1-z. C(2)–
H(2)ꢁꢁꢁO(1): C(2)–H(2), 0.93; H(2)ꢁꢁꢁO(1), 2.430; O(1)ꢁꢁꢁC(2),
and 2-(p-tolylazo)imidazolium ion. Fig. 4 represents molecular
view of the compound with the atom numbering scheme. The bond
lengths and bond angles are set out in Table 4. Data show slight
distortion from regular octahedron. The Pt–Cl distances appear in
between 2.31 to 2.33 Å. The Cl–Pt–Cl bond angles support regular
geometry of the ion (cis-Cl–Pt–Cl angles exist 89–90° and trans-
Cl–Pt–Cl angles are 179 to 180°). There are two 2-(p-tolylazo)imi-
dazolium ions (MeaaiH2+) to balance charge of the anion. These
two cations are in syn-configuration and two water molecules
are embedded in the channel of the ions. Both imidazole and p-to-
lyl fragments are planar. The N@N bond lengths are N(3)–N(4),
1.214(8) and N(7)–N(8), 1.197(11) Å. The separation is 0.017 Å
and is corroborated with literature data of other azoimidazole mol-
ecules [25–27]. Imidazolium ion is a good hydrogen bonding syn-
thon. In this ionic system potential hydrogen bond acceptor is
chloride (Cl in PtCl6). Besides, H2O in the molecule is a typical
3.299(9)
Å;\C(2)–H(2)ꢁꢁꢁO(1),
156.00°;
symmetry,
1 ꢀ x,
1 ꢀ y,1 ꢀ z. C(12)–H(12)ꢁꢁꢁCl(5): C(12)–H(12), 0.93; H(12)ꢁꢁꢁCl(5),
2.76(2); C(12)ꢁꢁꢁCl(5), 3.658(7);\C(12)–H(12)ꢁꢁꢁCl(5), 64.0°). Thus,
+
two MeaaiH2 is connected by hydrogen bonded H2O to form 1D
chain. Structure shows that each 1D chain is connected by hydro-
+
hydrogen bond donor and acceptor. Imidazolyl group of MeaaiH2
is hydrogen bonded with Cl of PtCl6 and embedded H2O (Fig. 5)
(viz., N(1)–H(1)ꢁꢁꢁCl(6): N(1)–H(1), 0.86; H(1)ꢁꢁꢁCl(6), 2.380;
N(1)Cl(6), 3.236(6) Å; \N(1)–H(1)ꢁꢁꢁCl(6), 176.00°; symmetry, 1 –
x, 2 – y,1 – z. N(2)–H(2a)ꢁꢁꢁO(1): N(2)–H(2a), 0.86; H(2a)ꢁꢁꢁO(1),
1.860; N(2)ꢁꢁꢁO(1), 2.714(7) Å;N(2)–H(2a)ꢁꢁꢁO(1), 176.00°. N(6)–
gen bonded H2O and face-to-face imidazoleꢁꢁꢁimidazole and p-
p
interactions (Figs. 5 and 6) (Cg1–Cg3a:4.005(4);
2ꢀ
tolylꢁꢁꢁp-tolylꢁꢁꢁ
Cg1–Cg3b: 3.873(4); Cg2–Cg4a: 3.789(4); Cg2–Cg4b:4.013(4)
where Cg(1): N(1),C(1,)C(2),N(2),C(3); Cg(2): C(4), C(5), C(6), C(7),
C(8), C(9); Cg(3): N(5), C(12), C(11), N(6), C(13); Cg(4): C(14),
C(15), C(16), C(17), C(18), C(19) where superscript a and b refer
to the motif in adjacent layers). Thus water molecule stitches
2ꢀ
two stacked ladder into a super ladder (Fig. 6). PtCl6 are posi-
Table 4
tioned in the sheets of hydrogen bonded and
p p interacted layers
ꢁꢁꢁ
Selected bond length (Å) and bond angles (°) of [MeaaiH2 H2O]2 [PtCl6]2ꢀ(15b).
+
2ꢀ
of [MeaaiH2.H2O]+. The intercalated anions PtCl6 are threaded by
hydrogen bonds with imidazolium N–H and H2O [O(1)–
H(1)ꢁꢁꢁCl(1): O(1)–H(1), 0.85; H(1)ꢁꢁꢁCl(1), 2.670; O(1)ꢁꢁꢁCl(1),
3.462(6) Å; \O(1)– H(1)—Cl(1), 155.00°; symmetry, 1-x,2-y,1-z.
O(2)–H(2B)ꢁꢁꢁCl(3): O(2)–H(2B), 0.92(6); H(2B)ꢁꢁꢁCl(3), 2.59(6);
O(2)ꢁꢁꢁCl(3), 3.507(6) Å; \O(2)–H(2B)—Cl(3), 175(10)°; symmetry,
1 ꢀ x, 2 ꢀ y, 1 ꢀ z. O(2)–H(2C)ꢁꢁꢁCl(4): O(2)–H(2C), 0.92(7);
H(2C)ꢁꢁꢁCl(4), 2.67(8); O(2)ꢁꢁꢁCl(4), 3.481(6) Å; \O(2)–H(2C)ꢁꢁꢁCl(4),
148(6)°; symmetry, 2 ꢀ x, 2 ꢀ y, 1 ꢀ z. O(1)–H(2)ꢁꢁꢁCl(4):
O(1)–H(2), 0.85; H(2)ꢁꢁꢁCl(4), 2.770; O(1)ꢁꢁꢁCl(4), 3.398(6) Å;
\O(1)–H(2)ꢁꢁꢁCl(4), 132.00°; symmetry, 2 ꢀ x,1 ꢀ y,1 ꢀ z. N(5)–
H(5a)ꢁꢁꢁCl(5): N(5)–H(5a), 0.86; H(5)ꢁꢁꢁCl(5), 2.480; N(5)ꢁꢁꢁ6 Cl(5),
Bond length (Å)
Bond angle (°)
Pt–Cl(1)
Pt–Cl(2)
Pt–Cl(3)
Pt–Cl(4)
Pt–Cl(5)
Pt–Cl(6)
N(3)–N(4)
N(7)–N(8)
2.3297(14)
2.3292(15)
2.3244(16)
2.3228(15)
2.3239(16)
2.3193(17)
1.214(8)
Cl(2)–Pt–Cl(1)
Cl(4)–Pt–Cl(1)
Cl(5)–Pt–Cl(1)
Cl(6)–Pt–Cl(1)
Cl(3)–Pt–Cl(2)
Cl(5)–Pt–Cl(3)
Cl(4)–Pt–Cl(5)
Cl(6)–Pt–Cl(5)
Cl(6)–Pt–Cl(4)
89.54(6)
179.18(6)
89.43(6)
90.47(6)
179.28(5)
90.25(7)
89.75(7)
179.81(6)
90.35(7)
1.197(11)
Fig. 5. Water molecule stitches two
alogn b-axis}.
p stacked ladder into a super ladder {viewed
-
2ꢀ
Fig. 6. Intercalated PtCl6
in the superladder.

2088
S. Halder et al. / Inorganica Chimica Acta 363 (2010) 2080–2088
[14] T.K. Misra, D. Das, C. Sinha, Polyhedron 16 (1997) 4163.
3.252(6) Å;
\N(5)–H(5a)ꢁꢁꢁCl(5),
149.00°;
symmetry,
[15] T.K. Misra, D. Das, C. Sinha, P.K. Ghosh, C.K. Pal, Inorg. Chem. 37 (1998) 1672.
[16] U.S. Ray, B. Chand, A.K. Dasmahapatra, G. Mostafa, T.–H. Lu, C. Sinha, Inorg.
Chem. Commun. 6 (2003) 634.
[17] K.K. Sarker, A.D. Jana, G. Mostafa, J.-S. Wu, T.–H. Lu, C. Sinha, Inorg. Chim. Acta
359 (2006) 4377.
2 ꢀ x,1 ꢀ y,1 ꢀ z. N(1)–H(1)ꢁꢁꢁCl(6): N(1)–H(1), 0.86; H(1)ꢁꢁꢁCl(6),
2.380; N(1)ꢁꢁꢁCl(6), 3.236(6) Å; \N(1)–H(1)ꢁꢁꢁCl(6), 176.00°; sym-
metry, 1 ꢀ x, 2 ꢀ y,1 ꢀ z]. Imidazole C–H is also playing important
role to stabilize hydrogen bonding interactions: C(12)–
H(12)ꢁꢁꢁCl(5): C(12)–H(12), 0.93; H(12)ꢁꢁꢁCl(5), 2.760; C(12)ꢁꢁꢁCl(5),
3.658(7); \C(12)–H(12)ꢁꢁꢁCl(5), 164.00° and contribute to generate
a ladder motif.
[18] N.N. Greenwood, A. Earnshaw, Chemistry of Elements, Butterworth,
Heinemann, London, 1997.
[19] G.M. Sheldrick,
SHELXS-97 Program for the Solution of Crystal Structure,
University of Gottingen, Germany, 1997.
[20] G.M. Sheldrick, SHELXL 97, Program for the Refinement of Crystal Structure,
University of Gottingen, Germany, 1997.
[21] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.
[22] A.L. Spek, PLATON, Molecular Geometry Program, University of Utrecht, The
Netherlands, 1999.
[23] J.P. Devlin, J. Sadle, V. Buchi, J. Phys. Chem. A 105 (2001) 974.
[24] N. Nishimura, T. Sueyoshi, H. Yamanaka, E. Imai, S. Yamamoto, S. Hasegawa,
Bull. Chem. Soc. Jpn. 49 (1976) 1381.
[25] P. Bhunia, B. Baruri, U.S. Ray, C. Sinha, S. Das, J. Cheng, T.–H. Lu, Transition Met.
Chem. 31 (2006) 310.
[26] J. Otsuki, K. Suwa, K. Narutaki, C. Sinha, I. Yoshikawa, K. Araki, J. Phys.Chem. A
109 (2005) 8064.
[27] J. Dinda, K. Bag, C. Sinha, G. Mostafa, T.–H. Lu, Polyhedron 22 (2003) 1367.
[28] S. Manikumaei, V. Shivaiah, S.K. Das, Inorg. Chem. 41 (2002) 6953.
[29] L.R. Macgillivary, J.L. Atwood, J. Am. Chem. Soc. 199 (1997) 22592.
[30] S. Supriya, S. Manikumari, P. Raghavaiah, S.K. Das, New J. Chem. 27 (2003)
218.
[31] S. Supriya, S.K. Das, New J.Chem. 27 (2003) 1568.
[32] J.N. Moorthy, R. Natarajan, P. Venugopalan, Angew. Chem., Int. Ed. 41 (2002)
3417.
4. Conclusion
1-Alkyl-2-(arylazo)imidazoles are low melting solids or gummy
mass. On acidification or alkylation they have been turned to ionic
solids [RaaiR/H+](Cl-) or [RaaiR02]+(Iꢀ). They are characterized by
elemental analyses and spectroscopic studies. X-Ray structure of
1-benzyl- 2-(phenylazo)imidazolium chloride shows hydrogen
bonded 1D chain. Each chain undergoes interaction with pendent
(1-CH2)Ph ring to constitute 2D network. Chlorometallates
[MCln]mꢀ also bind with dialkylated or protonated azoimidazolium
ions to give stable ionic solids. Tetrahedral [ZnCl4]2ꢀ and octahe-
dral [PtCl6]2ꢀ form interesting hydrogen bonded (D–HꢁꢁꢁA and C–
Hꢁꢁꢁ
p
) and
p p interacted superstructures. Two classes of com-
ꢁꢁꢁ
pounds are structurally characterized by single crystal X-ray dif-
[33] S.K. Ghosh, P.K. Bharadwaj, Inorg. Chem. 42 (2003) 8250.
[34] J.L. Atwood, L.J. Barbour, T.J. Ness, C.L. Raston, P.L. Raston, J. Am. Chem. Soc. 123
(2001) 7192.
fraction studies.
[35] R.J. Doedens, E. Yohannes, M.I. Kahn, Chem. Commun. (2002) 62.
[36] T.K. Prasad, M.V. Rajasekharan, Cryst. Growth Des. 6 (2006) 488.
[37] S.K. Ghosh, P.K. Bharadwaj, Eur. J. Inorg. Chem. 24 (2005) 4886.
[38] L.J. Barbour, G.W. Orr, J.L. Atwood, Nature 393 (1998) 671.
[39] L.J. Barbour, G.W. Orr, J.L. Atwood, Chem. Commun. (2000) 859.
[40] A. Michaelides, S. Skoulika, E.G. Bakalbassis, J. Mrozinski, Cryst. Growth Des. 3
(2003) 487.
Acknowledgments
Financial support from the University Grants Commission and
Council of Scientific and Industrial Research, New Delhi are grate-
fully acknowledged.
[41] R.D. Bergougant, A.Y. Robin, K.M. Fromm, Cryst. Growth Des. 5 (2005) 1691.
[42] S.K. Ghosh, P.K. Bharadwaj, Angew. Chem., Int. Ed. 43 (2004) 3577.
[43] S. Neogi, G. Savitha, P.K. Bharadwaj, Inorg. Chem. 43 (2004) 3771.
[44] S.K. Ghosh, J. Ribas, M.S.E. Fallah, P.K. Bharadwaj, Inorg. Chem. 44 (2005) 3856.
[45] S.K. Ghosh, P.K. Bharadwaj, Inorg. Chem. 43 (2004) 6887.
[46] K. Raghuraman, K.K. Katti, L.J. Barbour, N. Pillarsetty, C.L. Barnes, K.K. Katti,
J.Am. Chem. Soc. 125 (2003) 6955.
[47] P.S. Lakshminarayanan, E.I. Suresh, P. Ghosh, J. Am. Chem. Soc. 127 (2005)
13132.
[48] L.E. Cheruzel, M.S. Pometun, M.R. Cecil, M.S. Mashuta, R.J. Wittebort, R.M.
Buchanan, Angew. Chem., Int. Ed. 42 (2003) 5452.
Appendix A. Supplementary data
CCDC 246484, 637102, and 637103 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Center
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.ica.2010.02.006.
[49] S. Pal, N.B. Sankaran, A. Samanta, Angew. Chem., Int. Ed. 42 (2003) 1741.
[50] B. Sreenivasulu, J.J. Vittal, Angew. Chem., Int. Ed. 43 (2004) 5769.
[51] A. Mukiherjee, M.K. Saha, M. Nethaji, A.R. Chakravarty, Chem. Commun. (2004)
716.
References
[52] S. Banerjee, R. Murugavel, Cryst. Growth Des. 4 (2004) 545.
[53] M. Li, S. Chen, J. Xiang, H. He, L. Yuan, J. Sun, Cryst. Growth Des. 6 (2006) 1250.
[54] J.P. Naskar, M.G.B. Drew, A. Hulme, D.A. Tocher, D. Datta, Cryst. Eng. Comm. 7
(2005) 67.
[1] T.J. Mooibroek, C.A. Black, P. Gamez, J. Reedijk, Cryst. Growth Des. 8 (2008)
1082.
~
´
[2] A. Bianchi, K. Bowman-James, E. Garcıa-Espana (Eds.), Supramolecular
[55] B.-Q. Ma, H.-L. Sun, S. Gao, Chem. Commun. (2004) 2220.
[56] Layer X. Luan, Y. Chu, Y. Wang, D. Li, P. Liu, Q. Shi, Cryst. Growth Des. 6 (2006)
812.
Chemistry of Anions, Wiley, VCH, New York, 1997.
[3] Special Issue: 35 Years of Synthetic Anion Receptor Chemistry, Coord. Chem.
Rev. (2003) 240.
[57] D.L. Reger, R.F. Semeniuc, C. Pettinari, F. Luna-Giles, M.D. Smith, Cryst. Growth
Des. 6 (2006) 1068.
[4] I. Ravikumar, P.S. Lakshminarayanan, E. Suresh, Pradyut. Ghosh, Inorg. Chem.
47 (2008) 7992.
[58] A.K. Ghosh, D. Ghoshal, J. Ribas, G. Mostafa, N. Ray Chaudhuri, Cryst. Growth
Des. 6 (2006) 36.
[5] P.D. Beer, P.A. Gale, Angew. Chem., Int. Ed. 40 (2001) 486.
[6] J.M. Llinares, D. Powell, K. Bowman-James, Coord. Chem. Rev. 240 (2003) 57.
[7] J.L. Atwood, J.W. Steed, The Encyclopedia of Supramolecular Chemistry,
Dekker, New York, 2004.
[8] K. Bowman-James, K. Acc. Chem. Res. 38 (2005) 671.
[9] K. Wichmann, B. Antonioli, T. Söhnel, M. Wenzel, K. Gloe, J.R. Price, L.F. Lindoy,
A.J. Blake, E.A. Schröder, Coord. Chem. Rev. 250 (2006) 2987.
[10] Articles in Chem. Soc. Rev. 36 (2007) Issue 2.
[11] P.A. Gale, M.B. Hursthoure, T.A. Mayer, M.A. Paver, Chem. Commun. (2000)
275.
[59] L. Infantes, S. Motherwell, CrystEngComm 4 (2002) 454.
[60] L. Infantes, J. Chisholm, S. Motherwell, CrystEngComm 5 (2003) 480.
[61] B.G. Chand, U.S. Ray, J. Cheng, T.-H. Lu, C. Sinha, Polyhedron 22 (2003) 1213.
[62] B.G. Chand, U.S. Ray, G. Mostafa, T.–H. Lu, C. Sinha, Polyhedron 23 (2004) 1669.
[63] B.G. Chand, U.S. Ray, G. Mostafa, T.–H. Lu, C. Sinha, J. Coord. Chem. 57 (2004)
627.
[64] B.G. Chand, U.S. Ray, J. Cheng, T.–H. Lu, C. Sinha, Inorg. Chim. Acta 358 (2005)
1927.
[65] K. Deka, M. Lasker, J.B. Baruah, Polyhedron 25 (2006) 2525.
[66] C.-K. Lam, T.C.W. Mak, Chem. Commun. (2001) 1568.
[12] P.D. Beer, Chem. Commun. (1999) 1851.
[13] V.S. Bryantsev, B.P. Hay, Org. Lett. 7 (2005) 5031.