Synthesis, structure, photochromism, mesogenic property and DFT computations of silver(I) complexes of long chain alkyl group containing 1-alkyl-2-(arylazo)imidazoles

Article abstract of DOI:10.1016/j.poly.2014.04.066

The complexes [Ag(Raai-C_nH_{2n +1})₂]ClO₄ (where Raai-C_nH _2n+1 refer to 1-alkyl-2-(arylazo)imidazoles; R = H, Me and n = 4-22 (even numbers)) have been characterized by spectroscopic studies (UV-Vis, FT-IR, ¹H NMR). The X-ray structure of [Ag(Haai-C₂₂H₄₅)₂]ClO₄ confirms a distorted tetrahedral geometry. UV light irradiation (365-370 nm) of an acetonitrile solution of [Ag(Raai-C_nH_{2n +1})₂]ClO₄ shows E-to-Z (trans-to-cis) isomerization of the coordinated Raai-C_nH_{2 n+1} group. The reverse transformation, Z-to-E (cis-to-trans), is very slow upon visible light irradiation, but becomes significantly faster on increasing the temperature (298-313 K). The rates and quantum yields (φ_E→Z) of the E-to-Z isomerization of the free ligands are higher than those of the complexes, which have proved the effect of rotor volume, rotor mass and the 1-alkyl chain length (-C _nH_2n+1). [Ag(Haai-C ₁₈H₃₇)₂]ClO₄ shows a metallomesogenic property and undergoes phase transitions: the Cr (46.7 °C) - SmC (106.4 °C) - I phase sequence on heating and I (106.4 °C) - SmA (46.4 °C) - Cr on cooling. The SmC phase appears as the typical fan-shaped texture. DFT computations on the optimized structure were carried out to explain the spectral properties.

Full text of DOI:10.1016/j.poly.2014.04.066

Accepted Manuscript
Synthesis, Structure, Photochromism, Mesogenic property and DFT Computa-
tions of Silver(I) Complexes of Long Chain Alkyl Group Containing 1-Alkyl-2-
(arylazo)imidazoles
Avijit Nandi, Chandana Sen, Suman Roy, Debasish Mallick, Randhir Sinha,
Tapan Kumar Mondal, Chittaranjan Sinha
PII:
S0277-5387(14)00293-9
DOI:
http://dx.doi.org/10.1016/j.poly.2014.04.066
POLY 10710
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
11 December 2013
23 April 2014
Please cite this article as: A. Nandi, C. Sen, S. Roy, D. Mallick, R. Sinha, T.K. Mondal, C. Sinha, Synthesis, Structure,
Photochromism, Mesogenic property and DFT Computations of Silver(I) Complexes of Long Chain Alkyl Group
Containing 1-Alkyl-2-(arylazo)imidazoles, Polyhedron (2014), doi: http://dx.doi.org/10.1016/j.poly.2014.04.066
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1
Synthesis, Structure, Photochromism, Mesogenic property and DFT
Computations of Silver(I) Complexes of Long Chain Alkyl Group Containing
1-Alkyl-2-(arylazo)imidazoles
Avijit Nandi, Chandana Sen, Suman Roy, Debasish Mallick, Randhir Sinha, Tapan Kumar
Mondal and Chittaranjan Sinha*
Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata 700032,
India
Abstract
The complexes [Ag(Raai-CnH2n+1)2]ClO4 (where Raai-CnH2n+1 refer to 1-alkyl-2-
(arylazo)imidazoles; R = H, Me and n = 4-22 (even numbers)) have been characterized by
spectroscopic studies (UV-Vis, FT-IR, 1H NMR). The X-ray structure of [Ag(Haai-
C22H45)2]ClO4 confirms a distorted tetrahedral geometry. UV light irradiation (365-370 nm) of
an acetonitrile solution of [Ag(Raai-CnH2n+1)2]ClO4 shows E-to-Z (trans-to-cis) isomerization of
the coordinated Raai-CnH2n+1 group. The reverse transformation, Z-to-E (cis-to-trans), is very
slow upon visible light irradiation, but becomes significantly faster on increasing the temperature
(298-313 K). The rates and quantum yields (φE→Z) of the E-to-Z isomerization of the free ligands
are higher than those of the complexes, which have proved the effect of rotor volume, rotor mass
and the 1-alkyl chain length (-CnH2n+1). [Ag(Haai-C18H37)2]ClO4 shows a metallomesogenic
property and undergoes phase transitions: the Cr (46.7 °C) – SmC (106.4 °C) - I phase sequence
on heating and I (106.4 °C) – SmA (46.4 °C) - Cr on cooling. The SmC phase appears as the

2
typical fan-shaped texture. DFT computations on the optimized structure were carried out to
explain the spectral properties.
Keywords: Silver(I)-arylazoimidazoles, structure, photochromism, liquid crystal, nematic-
isotropic phase transition, Smectic phase
*Corresponding Author, Fax-+91-33-2414-6584, e-mail– c_r_sinha@yahoo.com (C. Sinha)
1. Introduction
Azobenzene, an interesting photochrome, undergoes a reversible E(trans)-Z(cis)
isomerization [1-5] upon light irradiation. Such a property of molecules has been used in
information storage, optical switching devices, surface relief gratings, non-linear optics etc [6-
11]. Arylazopyridine, an azoheterocycle, has several advantages [12-14] over azobenzene. These
compounds can bind Mn+/H+ with the pyridyl-N and/or the azo-N donor centre(s), which can
influence their properties. Binding with metal ions could minimize the problems of “fatigue” and
low durability of the organic photochrome. We have used 1-alkyl-2-(arylazo)imidazoles to
explore the coordination chemistry [15-20] and light stimulated properties [21-32]. The
photoisomerization of arylazoimidazole was first reported in 2003 [33] by T. Majima and
subsequent work had been done by us [21-32].
The synthesis of photosensitive liquid crystalline molecules [34, 35] is of present interest.
The combination of photochromism and liquid crystalline properties in the same molecule
provides an opportunity to explore a material which is useful for many practical applications
including imaging technology, optical storage materials, integrated optical devices, laser optical

3
media and non-linear optical (NLO) materials [36-40]. However, the synthesis of such materials
is challenging [41]. It is due to the loss of ordered orientation upon isomerisation of the rod-like
E configuration to the bent Z configuration [40]. Liquid crystalline (LC) phases exist in between
the three dimensionally ordered crystalline states and the disordered or isotropic fluid [37-41].
These are demanding problems in modern condensed matter chemistry and physics.
Recently, we have taken the initiative to include photochromism and liquid crystalline
properties in a single molecule, like 1-alkyl-2-(arylazo)imidazoles [42] by substituting a long
chain alkyl group at the imidazolyl part of the molecule. In this article, we wish to report the
Ag(I)-coordination complexes of 1-alkyl-2-(arylazo)imidazoles, Raai-CnH2n+1 (n = 4, 6, 8, 10,
12, 14, 16, 18, 20, 22). The characterisation has been carried out by spectroscopic data (IR, UV-
Vis, NMR) and structural confirmation has been carried out in one case by a single crystal X-ray
structure determination. Optical and thermal relaxation routes examine the photochromic
properties. The liquid crystalline properties are examined by polarising optical microscopy and
differential scanning calorimetry.
2. Experimental
2.1. Materials
AgClO4 was purchased from E. Merck. The analytical reagent grades materials 1-iodo-n-
butane, 1-bromo-n-hexane, 1-bromo-n-octane, 1-bromo-n-decane, 1-bromo-n-dodecane, 1-
bromo-n-tetradecane, 1-bromo-n-hexadecane, 1-bromo-n-octadecane, 1-bromo-n-icosane and 1-
bromo-n-docosane were purchased from Sigma-Aldrich and used as received. The 1-alkyl-2-
(arylazo)imidazoles were synthesized by the reported procedure [42]. All other chemicals and
solvents were reagent grade and used as received, and the solvents were purified before use by
standard procedures [43].

4
2.2. Physical measurements
Microanalytical data (C, H, N) were collected on a Perkin-Elmer 2400 CHNS/O elemental
analyzer. Spectroscopic data were obtained using the following instruments: UV-Vis spectra on a
Perkin Elmer Lambda 25 spectrophotometer; IR spectra (KBr disk, 4000-400 cm-1) on a Perkin
Elmer RX-1 FTIR spectrophotometer; photo excitation using a Perkin Elmer LS-55
1
spectrofluorimeter; H NMR spectra on a Bruker (AC) 300 MHz FTNMR spectrometer. The
liquid crystalline properties were established by thermal microscopy (Nikon polarizing
microscope LV100POL attached with a Linkam Temperature controlled stage model Examina-
THMS600) and the phase transitions were confirmed by differential scanning calorimetry
(Perkin Elmer Diamond DSC Pyris1 system).
2.2. The Synthesis of [Ag(Haai-C8H17)2]ClO4 (13a)
A solution of AgClO4 (0.18 g, 1.06 mmol) in dry MeOH (10 ml) was added in drops to a
stirred solution of Haai-C8H17 (0.40 g, 2.07 mmol) and the mixture was stirred in the dark for 2
h. A dark brown-red precipitate appeared. The mixture was further heated to dissolve the
precipitate and it was then filtered hot through a G-4 sintered glass crucible. An aqueous solution
of NaClO4 (0.5 g in 5 ml) was added with constant stirring to this solution. The precipitate so
obtained on cooling was collected by filtration, washed with water and recrystallised from 2-
methoxyethanol-MeOH (1:3, v/v) mixture. It was dried in vacuum and preserved in the dark.
Yield 0.54 g (66%).
Following identical procedures, the other [Ag(Raai-CnH2n+1)2]ClO4 (11-20) complexes were
prepared. Yield 60–75%.

5
The characterisation data of the complexes are as follows:
[Ag(Haai-C4H9)2]ClO4 (11a), Anal. found: C, 55.24; H, 5.77; N, 20.01. Calc. for
AgC26H32N8O4Cl: C, 55.33; H, 5.67; N, 19.86%. FTIR (KBr disc, cm-1): ν(N=N), 1380; ν(C=N),
1578. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 280 (12.0), 364 (18.5), 380 (29.3), 448
(2.4). [Ag(Meaai-C4H9)2]ClO4 (11b), Anal. found: C, 56.89; H, 6.50; N, 20.01. Calc. for
AgC28H36N8O4Cl: C, 56.77; H, 6.42; N, 18.92%. FTIR (KBr disc, cm-1): ν(N=N), 1384; ν(C=N),
1580. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 282 (13.1), 363 (18.2), 382 (16.0), 450
(3.4). [Ag(Haai-C6H13)2]ClO4 (12a), Anal. found: C, 58.00; H, 6.38; N, 17.95. Calc. for
AgC30H40N8O4Cl: C, 58.08; H, 6.45; N, 18.07%. FTIR (KBr disc, cm-1): ν(N=N), 1380; ν(C=N),
1576. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 286 (12.5), 365 (2.5), 380 (27.5), 451
(3.6) 286 (12.5). [Ag(Meaai-C6H13)2]ClO4 (12b), Anal. found: C, 59.20; H, 7.15; N, 17.22. Calc.
for AgC32H44N8O4Cl: C, 59.27; H, 7.10; N, 17.28%. FTIR (KBr disc, cm-1): ν(N=N), 1385;
ν(C=N), 1572. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 288 (13.2), 369 (19.1), 382
(16.8), 450 (2.2). [Ag(Haai-C8H17)2]ClO4 (13a), Anal. found: C, 60.43; H, 7.15; N, 16.48. Calc.
for AgC34H48N8O4Cl: C, 60.37; H, 7.10; N, 16.57%. FTIR (KBr disc, cm-1): ν(N=N), 1414;
ν(C=N), 1532. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 285 (12.5), 368 (18.9), 381
(29.8), 451 (2.7). [Ag(Meaai-C8H17)2]ClO4 (13b), Anal. found: C, 61.35; H, 7.54; N, 15.87. Calc.
for AgC36H52N8O4Cl: C, 61.38; H, 7.67; N, 15.91%. FTIR (KBr disc, cm-1): ν(N=N), 1384;
ν(C=N), 1568. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 284 (13.5), 365 (18.5), 382
(16.5), 450 (3.5). [Ag(Haai-C10H21)2]ClO4 (14a), Anal. found: C, 62.24; H, 7.58; N, 15.28. Calc.
for AgC38H56N8O4Cl: C, 62.31; H, 7.65; N, 15.30%. FTIR (KBr disc, cm-1): ν(N=N), 1380;
ν(C=N), 1572. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 285 (13.4), 366 (18.4), 381
(16.4), 452 (2.8). [Ag(Meaai-C10H21)2]ClO4 (14b), Anal. found: C, 63.10; H, 8.10; N, 14.46.

6
Calc. for AgC40H60N8O4Cl: C, 63.17; H, 8.16; N, 14.54%. FTIR (KBr disc, cm-1), ν(N=N), 1385;
ν(C=N), 1570. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 286 (13.2), 367 (18.7), 384
(16.2), 453 (3.5). [Ag(Haai-C12H25)2]ClO4 (15a), Anal. found: C, 63.92; H, 8.10; N, 14.13. Calc.
for AgC42H64N8O4Cl: C, 63.97; H, 8.12; N, 14.21. FTIR (KBr disc, cm-1): ν(N=N), 1376;
ν(C=N), 1578. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 302 (9.1), 365 (17.6), 379
(16.1), 450 (1.4). [Ag(Meaai-C12H25)2]ClO4 (15b), Anal. found: C, 64.09; H, 8.16; N, 14.09.
Calc. for AgC44H68N8O4Cl: C, 63.97; H, 8.12; N, 14.21%. FTIR (KBr disc, cm-1): ν(N=N), 1375;
ν(C=N), 1578. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 296 (11.4), 368 (18.4), 383
(17.0), 454 (2.1). [Ag(Haai-C14H29)2]ClO4 (16a), Anal. found: C, 65.38; H, 8.48; N, 13.15. Calc.
for AgC46H72N8O4Cl: C, 65.41; H, 8.53; N, 13.27%. FTIR (KBr disc, cm-1): ν(N=N), 1380;
ν(C=N), 1566. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 285 (11.2), 367 (18.5), 382
(16.9), 453 (2.3). [Ag(Meaai-C14H29)2]ClO4 (16b), Anal. found: C, 66.00; H, 8.99; N, 12.74.
Calc. for AgC48H76N8O4Cl: C, 66.07; H, 8.94; N, 12.84%. FTIR (KBr disc, cm-1): ν(N=N), 1388;
ν(C=N), 1578. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 284 (11.3), 366 (18.9), 381
(15.9), 452 (2.5). [Ag(Haai-C16H33)2]ClO4 (17a), Anal. found: C, 66.62; H, 8.97; N, 12.37. Calc.
for AgC50H80N8O4Cl: C, 66.68; H, 8.89; N, 12.42%. FTIR (KBr disc, cm-1): ν(N=N), 1385;
ν(C=N), 1573. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 302 (8.1), 365 (11.9), 378
(10.8), 456 (1.2). [Ag(Meaai-C16H33)2]ClO4 (17b), Anal. found: C, 67.18; H, 9.23; N, 12.00.
Calc. for AgC52H84N8O4Cl: C, 67.25; H, 9.26; N, 12.07%. FTIR (KBr disc, cm-1): ν(N=N), 1381;
ν(C=N), 1568. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 285 (8.9), 368 (17.2), 377
(16.8), 458 (2.2). [Ag(Haai-C18H37)2]ClO4 (18a), Anal. found: C, 67.70; H, 9.13; N, 11.64. Calc.
for AgC54H88N8O4Cl: C, 67.79; H, 9.20; N, 11.71%. FTIR (KBr disc, cm-1): ν(N=N), 1387;

7
ν(C=N), 1568. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 289 (9.6), 365 (17.9), 375
(16.7), 450 (2.5). [Ag(Meaai-C18H37)2]ClO4 (18b), Anal. found: C, 68.23; H, 9.50; N, 11.29.
Calc. for AgC56H92N8O4Cl: C, 68.30; H, 9.55; N, 11.38%. FTIR (KBr disc, cm-1): ν(N=N), 1377;
ν(C=N), 1577. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 287 (11.2), 367 (18.2), 378
(16.8), 457 (2.3). [Ag(Haai-C20H41)2]ClO4 (19a), Anal. found: C, 68.75; H, 9.45; N, 11.00. Calc.
for AgC58H96N8O4Cl: C, 68.78; H, 9.48; N, 11.06%. FTIR (KBr disc, cm-1): ν(N=N), 1414;
ν(C=N), 1572. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 290 (12.2), 366 (2.4), 382
(27.3), 458 (3.3). [Ag(Meaai-C20H41)2]ClO4 (19b), Anal. found: C, 69.17; H, 9.88; N, 10.69.
Calc. for AgC60H100N8O4Cl: C, 69.24; H, 9.80; N, 10.77%. FTIR (KBr disc, cm-1): ν(N=N), 1379;
ν(C=N), 1574. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 288 (11.1), 366 (18.7), 383
(15.3), 450 (2.8). [Ag(Haai-C22H45)2]ClO4 (20a), Anal. found: C, 69.62; H, 9.65; N, 10.40. Calc.
for AgC62H104N8O4Cl: C, 69.67; H, 9.73; N, 10.48%. FTIR (KBr disc, cm-1): ν(N=N), 1384;
ν(C=N), 1567. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 288 (4.8), 367 (16.3), 381
(16.7), 453 (2.0). [Ag(Meaai-C22H45)2]ClO4 (20b), Anal. found: C, 70.00; H, 10.09; N, 10.12.
Calc. for AgC64H108N8O4Cl: C, 70.08; H, 10.03; N, 10.22%. FTIR (KBr disc, cm-1): ν(N=N),
1380; ν(C=N), 1573. UV/Vis (MeCN) (λmax, nm (10-3 ε, dm3 mol-1 cm-1): 292 (15.1), 367 (16.0),
382 (14.1), 456 (1.5).
2.3. X-ray diffraction study
Crystals of [Ag(Haai-C22H45)2]ClO4 (20a) (0.20 x 0.14 x 0.08 mm) were grown by slow
diffusion of a dichloromethane solution into hexane at ambient conditions for a week. A suitable
single crystal was mounted on a Siemens CCD diffractometer equipped with graphite
monochromated Mo-Kα (λ = 0.71073 Å) radiation. The crystallographic data are shown in Table

8
1. Unit cell parameters and crystal-orientation matrices were determined from the least-squares
method in the range -12 ≤ h ≤ 12, -10 ≤ k ≤ 10, -40 ≤ l ≤ 40 and angle varying in the range 1.87 <
θ < 24.80°. The intensity data were corrected for Lorentz and polarisation effects and an
empirical absorption correction was also employed using the SAINT program. Data were
collected applying the condition I > 2σ(I). The structure was solved by direct methods and
followed by successive Fourier and difference Fourier syntheses. Full matrix least squares
refinements on F2 were carried out using SHELXL-97 [44] with anisotropic displacement
parameters for all non-hydrogen atoms. Hydrogen atoms were constrained to ride on their
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 factors were used throughout for all cases. The maximum (∆max, e Å-3) and minimum
(∆min, e Å-3) electron densities are 0.942 and -0.613. All calculations and drawings were carried
out using SHELXL 97 [44], SHELXS 97 [45], PLATON 99 [46] and ORTEP-3 [47] programs.
2.4. Photometric measurements
Absorption spectra were taken with a Perkin Elmer Lambda 25 UV/VIS
spectrophotometer in a 1 x 1 cm quartz optical cell maintained at 25 °C with a Peltier thermostat.
The light source of a Perkin Elmer LS 55 spectrofluorimeter was used as an excitation light, with
a slit width of 10 nm. An optical filter was used to cut off overtones when necessary. The
absorption spectra of the cis isomers were obtained by extrapolation of the absorption spectra of
1
a cis-rich mixture for which the composition is known from H NMR integration. Quantum
yields (φ) were obtained by measuring the initial trans-to-cis isomerization rates (ν) in a well-
stirred solution within the above instrument using the equation, ν = (φ I0 /V)(1- 10-Abs) where I0 is
the photon flux at the front of the cell, V is the volume of the solution, and Abs is the initial

9
absorbance at the irradiation wavelength. The value of I0 was obtained by using azobenzene (φ =
0.11 for π-π* excitation [48]) under the same irradiation conditions.
The thermal E-to-Z (cis-to-trans) isomerisation rates were obtained by monitoring
absorption changes intermittently for a cis-rich solution kept in the dark at constant temperatures
(T) in the range 298-313 K. The activation energy (Ea) and the frequency factor (A) were
calculated from ln k = ln A –Ea/RT, where k is the measured rate constant, R is the gas constant
and T is the temperature. The values of the activation free energy (∆G*) and activation entropy
(∆S*) were obtained through the relationships ∆G* = Ea –RT-T∆S* and ∆S* = [ln A -1-
ln(kBT/h)/R], where kB and h are Boltzmann’s and Plank’s constants, respectively.
2.5. Computational methods
All the calculations were carried out with the density functional theory (DFT) method as
implemented in the GAUSSIAN 03 program package for the optimized geometry of [Ag(Haai-
C22H45)2]ClO4 (20a) using the crystallographic information file [49]. The hybrid DFT-B3LYP
functional was used in the calculations [50]. For C, H, N, O and Cl, the 6-31G(d) basis set was
assigned. The Los Alamos effective core potential plus double zeta (LanL2DZ) [51] basis set
along with the corresponding pseudo potential without any symmetry constrains were used for
silver. A vibrational frequency calculation was also performed for two complexes to ensure that
the optimized geometries represent the local minima and there are only positive Eigen values. To
assign the low lying electronic transitions in the experimental spectra, TDDFT calculations of the
complexes were done in the gas phase. We have attempted TD-DFT calculations in acetonitrile
solvent using a conductor-like polarizable continuum model (CPCM) [52–54], however these
failed due to the huge number of functional parameters for such a large molecule on a desktop
computer. We computed the lowest 25 singlet-singlet transitions and the results of the TD-DFT

10
calculations were qualitatively very similar. GaussSum [55] was used to calculate the fractional
contributions of various groups to each molecular orbital.
3. Results and Discussion
3.1. Synthesis and formulation
1-Alkyl-2-(arylazo)imidazole (Raai-CnH2n+1) has been synthesized by the alkylation of 2-
(arylazo)imidazole (Raai-H) by controlled addition of alkyl halide (CnH2n+1X) in dry THF using
NaH [42] (Scheme 1). Alkyl halides of varying carbon chain length (C4 to C22) have been used to
synthesize Raai-CnH2n+1 (R = H (a), Me (b); n = 4 (C4H9, 1), 6 (C6H13, 2), 8 (C8H17, 3), 10
(C10H21, 4), 12 (C12H25, 5), 14 (C14H29, 6), 16 (C16H33, 7), 18 (C18H37, 8), 20 (C20H41, 9), 22
(C22H45, 10)). Raai-CnH2n+1 has been used for the synthesis of silver(I) complexes [Ag(Raai-
CnH2n+1)2](ClO4) (11-20). The complexes were purified by diffusion of a dichloromethane
solution into layered hexane. The molar conductance data (ΛM, 120-160 Ω-1 mol-1) correspond to
1:1 electrolyte character in acetonitrile solution and their composition has been supported by
microanalytical data. The structural confirmation has been achieved by a single-crystal X-ray
diffraction study of [Ag(Haai-C22H45)2]ClO4 (20a). Other spectroscopic techniques (FTIR, UV-
1
Vis, H NMR) have been used to characterize the complexes. Mass spectral have not been
collected due to the typical problem of the explosive nature of the complexes.

11
+
N
N
N
N
N
CnH2n+1
H2n+1Cn
Ag
N
N
N
R
R
Raai-CnH2n+1 (1 -10)
[Ag(Raai-CnH2n+1 )2]+ (11-20)
R = H (a), Me (b); CnH2n+1 for n = 4 (1), 6 (2), 8 (3), 10 (4), 12 (5), 14 (6), 16 (7), 18 (8), 20 (9),
22 (10); [Ag(Haai-C4H9)2]ClO4 (11a), [Ag(Meaai-C4H9)2]ClO4 (11b), [Ag(Haai-C6H13)2]ClO4
(12a), [Ag(Meaai-C6H13)2]ClO4 (12b) , [Ag(Haai-C8H16)2]ClO4 (13a), [Ag(Meaai-C8H16)2]ClO4
(13b), [Ag(Haai-C10H21)2]ClO4 (14a), [Ag(Meaai-C10H21)2]ClO4 (14b), [Ag(Haai-C12H25)2]ClO4
(15a), [Ag(Meaai-C12H25)2]ClO4 (15b), [Ag(Haai-C14H29)2]ClO4 (16a), [Ag(Meaai-
C14H29)2]ClO4 (16b), [Ag(Haai-C16H33)2] ClO4 (17a),
[Ag(Meaai-C16H33)2]ClO4 (17b),
[Ag(Haai-C18H37)2]ClO4 (18a), [Ag(Meaai-C18H37)2]ClO4 (18b), [Ag(Haai-C20H41)2]ClO4 (19a),
[Ag(Meaai-C20H41)2]ClO4 (19b), [Ag(Haai-C22H45)2]ClO4 (20a), [Ag(Meaai-C22H45)2]ClO4
(20b)
Scheme 1. Raai-CnH2n+1 (1-10) and [Ag(Raai-CnH2n+1)2]ClO4 (11-20)
3.2. Molecular structures
The molecular structure of [Ag(Haai-C22H45)2]ClO4 (20a) is shown in Fig. 1. The bond
parameters are listed in Table 2. Haai-C22H45 acts as an N,N/-chelating ligand where N and N/

12
of
refer to N(imidazole) and N(azo) donor centres and the chelate angle
67.44(12)° is close to reported data [56,57]. The constituents of the chelate plane Ag(1)–N(2)–
C(1)–N(3)–N(4) show torsion angles in the range 2.2-4.0°. The two chelate planes about Ag(I)
are inclined at 52.55(16)°. Other bond angular values are ∠Ag(1)-N(2)-C(1), 120.0(3)° and
∠Ag(1)-N(4)-N(3), 111.7(2)°. The Ag-N(imidazolyl) bond length (2.146(4) Å) is shorter than
the Ag-N(azo) bond length (2.650(4) Å), which reflects the stronger interaction between Ag(I)
and N(imidazolyl). The Ag-N(imidazolyl) distances in this example are longer than previously
reported data of [Ag(α-NaiEt)2]ClO4 (α-NaiEt = 1-ethyl-2-(naphthyl-α-azo)imidazole; Ag-
N(imidazolyl), 2.124(5)/2.128(5) Å) while the Ag-N(azo) bond length is shortened by 0.3 Å
compared to the reported result (2.851(5) Å) [57]. The pendant phenyl ring is no longer planar
with the chelate plane of Ag(1)–N(2)–C(1)–N(3)–N(4) and is inclined at an angle of 13.6(2)°.
-
Imidazolyl-H (3-H) forms a hydrogen bond with O-ClO3 to give a supramolecule (C(3)–H(3)---
O(2): H(3)---O(2), 2.490(3) Å; C(3)----O(2), 3.262(11) Å and ∠C(3)–H(3)---O(2), 141.00°;
symmetry, -1+x, 1+y, z). The packing view shows interdigitation of alkyl C-H bonds of the long
chain alkyl group and the dispersion force may hold these units together (Fig. 2). The DFT
calculated optimized structure of the E-isomer (20a) shows structural compatibility with the
experimentally determined structure (Table 2). We could not isolate a crystal of the Z-isomer
(20a/), however the structural parameters from optimized geometry (DFT technique) show
elongation of bond lengths and angles, which may be due to the structural strain developed in the
arrangement.
3.3. The spectral characterization

13
The infrared spectral bands of the –N=N– and –C=N– groups of Raai-CnH2n+1 appear at
1400-1410 and 1620-1625 cm-1 respectively. The complexes [Ag(Raai-CnH2n+1)2]ClO4 show
moderately intense stretches at 1565-1580 and 1370-1385 cm-1 which are due to ν(C=N) and
ν(N=N), respectively. DFT computation of the optimized structure of [Ag(Haai-C22H45)2]ClO4
has been carried out and a vibrational frequency calculations were performed; the main
frequencies have been compared between the calculated and experimental data. The stretching
frequencies shifting to a lower frequency region in the complexes are in support of coordination
of the azo-N and imine-N atoms to Ag(I) [57].
1
The H NMR spectra of the complexes were recorded in CDCl3. The atom numbering
pattern is shown in Scheme 1. The alkylation of the imidazolyl motif at 2-(arylazo)imidazole is
supported by the disappearance of δ(N–H) at ~10.30 ppm and the appearance of an N(1)-alkyl
signal at 0.85- 4.40 ppm; -N–CH2 –(CH2)n –CH3 shows a triplet for –CH2– at 4.40 ppm and
multiplet for –(CH2)n– at 1.22-1.90 ppm [42]. The imidazolyl 4- and 5-H protons appear as broad
singlets at 7.24-7.28 and 7.14-7.17 ppm, respectively. Broadening may be due to rapid proton
exchange between these protons. The aryl protons (7-H to 11-H) are upfield shifted on going
from Haai-CnH2n+1 (1a-10a) to Meaai-CnH2n+1 (1b-10b), which may be due to the +I effect of the
Me group in the aryl part. The data (Table 3) reveal that the signals in the spectra of the
complexes are shifted downfield relative to the free ligand values. This supports the coordination
of the ligand to Ag(I) [56,57]. The imidazolyl protons (4-H and 5-H) suffer downfield shifting by
0.3-0.4 ppm compared to the free ligand positions. This supports the strong preference of
imidazolyl-N binding to Ag(I).
3.4. The absorption spectra and photochromism

14
The absorption spectra were recorded in MeOH solution for the ligands and in MeCN
solution (because of the sparing solubility of the complexes in MeOH) for the complexes, over
the wavelength range 200-600 nm. The absorption spectra of the ligands Raai-CnH2n+1 show
transitions at 270-290 and 360-390 nm (ε, 104 M-1 cm2) and a tail with a weak band at 450-460
nm. The intense absorption band at 270-290 nm corresponds to π-π* transitions localized on the
phenyl group, the band at 360 nm originates from symmetry-allowed π-π* transitions and the
band at 450 nm corresponds to an n-π* transition [21]. In the solution spectra of [Ag(Raai-
CnH2n+1)2]ClO4 (11-20), the absorption maxima (λmax) are shifted to a longer wavelength region
by 4-10 nm compared to the free Raai-CnH2n+1 data. This defines the coordination of Raai-
CnH2n+1 to Ag(I) [57]. The effect of the chain length of the alkyl group (-CnH2n+1) on the
transition wavelength is difficult to rationalize, however there is a general trend that λmax
increases with an increase in the number of carbon atoms (n) in the chain of -CnH2n+1 in the
ligand.
The irradiation of UV light at λmax (selected from the π--π* band of the UV-Vis spectra)
to a MeOH solution of the ligands, and an acetonitrile solution of the complexes gives the
spectral change shown in Fig. 3. Ag(I) compounds are, in general, sensitive to light and undergo
photoreduction to metallic Ag [58]. However, in many coordination complexes with delocalized
π-electrons or accessible molecular vibration or rotation, the photon energy (hν) may be used for
these additional activities instead of the photoredox reaction [56,57]. The spectra of irradiated
solutions show that the intense peak at λmax decreases, and this is accompanied by a slight
increase at the tail portion of the spectra, around 525 nm, until a stationary state is reached. The
state is defined as photostationary state I (PSS-I) activated by the π--π* transition. Subsequent
irradiation at the newly appeared longer wavelength peak reverses the course of the reaction

15
slowly and the original spectra are recovered up to a point, which is another photostationary state
II (PSS-II, n--π* transition) under irradiation at the longer wavelength peak. The quantum yields
of the E-to-Z photoisomerization were determined using those of azobenzene [48] as a standard
and the results are tabulated in Table 4. The photoisomerisation of the ligands in the complexes
is dependent on the nature of metal ion, its oxidation state and the structural state [21-26]. It is
observed that upon UV light irradiation the E-to-Z photoisomerisation proceeds and a Z molar
ratio reaches ~ 75%. The absorption spectra of the E-isomers have changed, with isosbestic
points upon excitation (Fig. 3), into the Z-isomer. The ligands and the complexes show little sign
of degradation upon repeated irradiation with up to at least 15 cycles in each case. The quantum
yields were measured for the trans-to-cis (φt→c) photoisomerisation of complexes in acetonitrile
on irradiation with UV wavelength light (Table 4). The φE→Z values are significantly dependent
on the chain length, -CnH2n+1; an increase in the chain length decreases the rate of E-to-Z isomer
transformation. The Me substituent at the azoaryl group (Haai-CnH2n+1 to Meaai-CnH2n+1) and
substituents at the N(1)-position both reduce the φE→Z values. In general, an increase in mass of
the molecule reduces the rate of isomerisation. In the complexes, the φE→Z values are
significantly less than those of the free ligand data. It may be argued that the reasons for this
decrement are (i) the presence of a coordinated Ag(I) motif which increases the molar mass of
the unit and may interfere with the motion of the –N=N-Ar moiety and (ii) the increase of the
alkyl chain length N(1)-CnH2n+1 which interferes with the motion of the -N=N-Ar moiety, in
addition to the small increase in molar mass (14 per –CH2- unit). The rotor volume has
significant influence on the isomerisation rate and quantum yields [21-32].
Thermal isomerisation was carried out in the dark by UV-Vis spectroscopy in MeOH
(ligand) and in MeCN (complexes) at varied temperatures, 298-308 K. The Eyring plots gave a

16
linear graph from which the activation energy was obtained (Table 5, Fig. 4). In the complexes,
the Ea values are severely reduced, which means faster Z-to-E thermal isomerisation. The
entropies of activation (∆S*) are more highly negative in the complexes than in the free ligands.
This is also in support of an increase in rotor volume in the complexes. The activation energy
(Ea) deceases significantly with an increase in alkyl chain length (Fig. 5).
N
N
N
Ag
N
N
N
N
N
N
Ag
Ag
H2n+1Cn
H2n+1Cn
H2n+1Cn
N
N
R
N
R
R
E- or trans-
Z- or cis-
Scheme 2. Plausible mechanism of the photoisomerisation of coordinated Raai-CnH2n+1 in
[Ag(Raai-CnH2n+1)2]+
A plausible mechanism for photoisomerisation may be accounted for by cleavage of the Ag-
N(azo) bond, retaining the Ag-N(imidazolyl) bond, followed by rotation of the excited state
about the free –N=N- bond (Scheme 2). Sustenance of the Ag-N(imidazolyl) bond may be
supported by the photostability of these complexes, even after prolonged irradiation in the
solution phase [58]. The DFT calculated results of the optimized geometries of representative
complexes, the E-isomer of [Ag(E-Haai-C22H45)2]ClO4 (20a) and Z-isomer of [Ag(Z-Haai-
C22H45)2]ClO4 (20a/), have been used to interpret the absorption spectra in the gas phase and to

17
explain the photoisomerisation. The optimized structure of the E-isomer is more stable than the
Z-isomer by 125.51 Kcal mol-1 (Fig. 6). In the case of the E-isomer, the HOMO (highest
occupied molecular orbital) (-8.26 eV), HOMO-1 (-8.26 eV); HOMO-2 (-8.82 eV), HOMO-3 (-
8.82 eV); HOMO-4 (-8.88 eV), HOMO-5 (-8.88 eV) (Fig. 7) are degenerately paired; other
lower energetic filled MOs are closely spaced (Supplementary Material, Fig. S1). The LUMO
(lowest unoccupied molecular orbital) (-5.48 eV) and LUMO+1 (-5.47 eV) are also nearly
degenerate. There is a large energy gap between LUMO+1 (-5.47 eV) and LUMO+2 (-2.80 eV),
and other LUMO+m (m = 3, 4 5 etc) appear within -2.8 to -2.4 eV (Supplementary Materials;
Fig. S2). The MOs of the Z-isomer are distributed as follows: HOMO (-7.75 eV), HOMO-1 (-
7.86 eV), HOMO-2 (-8.29 eV), LUMO (-5.82 eV), LUMO+1 (-5.68 eV), LUMO+2 (-3.23 eV)
etc (Supplementary Materials; Fig. S3). The HOMO is stabilized by 0.51 eV (11.76 Kcal) in the
E-isomer, while the LUMO is stabilized by 0.34 eV (7.84 Kcal) in the Z-isomer. The carbon of
the alkyl chain (-C22H45) partly contributes to the HOMO and HOMO-1 (99%) of the E-isomer,
while HOMO-3, HOMO-4 and others are comprised of the 2-(phenylazo)imidazolyl (Haai-)
motif (> 80%) (Supplementary Material, Table S1). The unoccupied MOs (LUMO, LUMO+1
etc.) are composed mainly of the Haai- motif. The composition and energy of the MOs are given
in the Supplementary Material (Figs. S1, S2, Tables S1, S2). High intense bands calculated at
430.83 (oscillator strength f, 0.0166), 384.4 (f, 0.1694), 382.04 (f, 0.6257) and 379.11 nm (f,
0.4894) are referred to the HOMO-3 → LUMO, HOMO-4 → LUMO+1, HOMO-3 → LUMO+1
and HOMO-6 → LUMO+1 transitions, respectively, and have been assigned mainly to intra-
ligand charge transfer (ILCT) bands. The transition at 379.64 nm (f, 0.0366) is assigned to the
HOMO-5 → LUMO+1 transition, and refers to CRCT (chain to ring charge transfer). The
HOMO → LUMO+6 transition at 322 nm is assigned to a ligand-to-metal charge transfer

18
-
(LMCT) transition. Higher energy transitions < 300 nm are associated with ClO4 and the Haai-
motif (Supplementary Materials, Tables S3). The HOMO-LUMO energy separation (∆E = 0.85
eV or 19.60 Kcal mol-1) also indicates the generation of a low energy band (~420 nm) upon UV
light irradiation, which indicates a population increment for the Z-isomer (Fig. 3).
In the photochromic process irradiation with UV light isomerizes the more stable trans-
isomer (E) to the cis-isomer (Z). Irradiation in the UV region causes a π→π* transition which is
responsible for cleavage of the Ag-N(azo) bond and opening of the chelate ring, followed by the
E → Z geometry change. The LMCT (ligand-to-metal charge transition) or CRCT (chain-to-ring
charge transition) are lower energetic transitions and are insufficient to perform bond cleavage
and isomerisation. Conversely, the metallated ligand may perform a charge transition in a
secondary (LMCT or CRCT) process, which is responsible for deactivation of the excited species
and regulates the rate of isomerisation and quantum yields (Table 4).
To further study the electronic structure, NBO calculations on the optimized geometry of
the Z-isomer of [Ag(Haai-C22H45)2]ClO4 (20a) have been performed. The polarity of the bonds is
accounted for by Natural Bond Orbital (NBO) analysis (Supplementary Table S5). The Ag-N
bonds have one natural bond orbital; the NBO charge of the Ag centre is 0.624, which is lower
than the +1 formal oxidation state. The charges on imidazolyl-N are -0.400 (N(1)) and -0.643
(N(2)), while the N(azo) atoms show charges of -0.266 (N(3)) and -0.219 (N(4)). The data imply
that a stronger interaction exists between Ag and imidazoly-N, than between Ag and azo-N. The
preferential cleavage of the Ag-N(azo) bond upon light irradiation may thus be rationalized.
3.5. Metallomesogenic properties

19
The thermal properties of [Ag(Raai-CnH2n+1)2]ClO4 were examined using polarized light
optical microscopy (POM) and differential scanning calorimetry (DSC). The mesogenic property
of Raa-CnH2n+1 has been reported by us [42]. Haai-C18H37 exhibits a nematic (N) texture at 55
°C and Haai-C22H45 shows an unknown Smectic (Sm) phase at 62 °C. On cooling, the isotropic
phase of Haai-C18H37 transforms to the ‘Schlieren’ phase.
A textural analysis of [Ag(Raai-CnH2n+1)2]ClO4 has been performed by polarizing optical
microscopy (POM). A significant response was observed for [Ag(Haai-C18H37)2]ClO4 (18a) (Fig.
8). Complex 18a shows the phase sequence Cr – SmC- I. On cooling, the isotropic phase of 18a
shows the phase sequence I – SmA- Cr. The SmC phase appears as a typical fan-shaped texture
[34,37,41] (Fig 8b) when placed in a thin cell with a cell gap of d = 5
0.2 µm under
homogeneous planar boundary conditions. On cooling the isotropic liquid, the Smectic phase
forms a fan-shaped texture, which is more reminiscent of a SmA phase than a SmC phase (Fig.
8d). The other complexes do not show any mesomorphic phase sequences.
Differential scanning calorimetry (DSC) was used to measure the phase transition energy.
In case of complex 18a, a large value of ∆H (160.97 J/g) was observed, which occurs at a phase
transition at 106.4 °C. This peak clearly indicates that a transition takes place from the SmC
phase to an isotropic phase. A small peak arises at 46.7 °C, where ∆H is very low (6.3 J/g),
indicating a transition from a crystal phase to the SmC phase (Fig. 9). Upon cooling, the complex
shows a phase transition around 46.4 °C to the SmA phase and here the enthalpy is (5.3 J/g).
From the above information it is clear that both exothermic and endothermic changes take place.
Conclusions

20
The complexes [Ag(Raai-CnH2n+1)2]ClO4 have been structurally established. Raai-CnH2n+1 shows
E(trans)-to-Z(cis) isomerisation upon UV-light irradiation both in the free and coordinated states.
Photochromism of the complexes show a weaker response compared to the free ligand data. The
rates and quantum yields of the E-to-Z isomerisation of the complexes are lower than the free
ligands. The Z-to-E isomerisation is a thermally driven process. The activation energies (Eas) are
found to be lower and ∆S* more highly negative in the complexes than the free ligands. The
slow rate of isomerisation in the complexes may be due to a higher rotor volume and mass than
for the free ligands. One of the complexes, [Ag(Haai-C18H37)2]ClO4, shows a metallomesogenic
property and undergoes phase transitions: the Cr (46.7 °C) – SmC (106.4 °C) – I phase sequence
on heating and I (106.4 °C) – SmA (46.4 °C) – Cr on cooling. The SmC phase appears with a
typical fan-shaped texture.
Supplementary material
Crystallographic data for the structures have been deposited with the Cambridge
Crystallographic Data Center, CCDC No. 967552. Copies of this information may be obtained
free of charge from the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. (e-mail,
deposit@ccdc.cam.ac.uk or www, htpp://www.ccdc.cam.ac.uk).
Acknowledgements
The authors express their sincere thanks to the Department of Science and Technology (DST)
and the Council of Scientific and Industrial Research, New Delhi and Kolkata for financial
support. One of the authors (AN) thanks UGC for the award of a Fellowship.

21
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87

26
Table 1. Summarized crystallographic data for [Ag(Haai-C22H45)2]ClO4 (20a)
20a
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
C62H104N8O4ClAg
1168.85
293(2)
Monoclinic
P2/c
10.927(5)
8.656(5)
34.203(5)
92.778(5)
3231(2)
2
b (Å)
c (Å)
β (°)
V (Å)3
Z
µ (MoKα) (mm-1)
Dcalc (Mg m-3)
Refine parameters
Total reflections
Unique reflections
0.402
1.201
344
42980
5516
a
0.0658
R1 [ I > 2σ (I) ]
b
wR2
0.1926
Goodness of fit
1.037
a
b
2
2 2 1/2
R=ΣFo-Fc/ΣFo. wR2 = [Σw(Fo -Fc2)2/ Σw(Fo ) ] , w = 1/[σ2(F0)2+ (0.1121P)2]
2
where P = (F0 + 2Fc2) / 3 .

27
Table 2. Experimental and theoretical bond distances (Å) and angles (°) of some selected bonds
in [Ag(E-Haai-C22H45)2]ClO4 (20a) and [Ag(Z-Haai-C22H45)2] ClO4 (20a/)≠
Bond distances (Å)
Bond angles (°)
20a/
20a/
Theo
20a
20a
Bonds
Expm
Theo Theo
Angles
Expm
Theo
N(1)-C(1)
1.352(6) 1.382 1.403 C(4)-C(5)-C(6)
113.0(4) 111.618 113.251
111.6(4) 112.627 116.549
N (1)-C(3) 1.354(6) 1.384 1.407 C(5)-C(6)-C(7)
C(2)-C(3)
Ag(1)–N(2) 2.146(4) 2.197 2.214 C(23)-C(24)-C(25) 115.0(5) 113.012 115.210
1.362(6) 1.395 1.415 C(22)-C(23)-C(24) 115.4(4) 113.319 120.322
Ag(1)-N(4) 2.650(4) 2.728 2.845 Ag(1)-N(2)-C(1)
N(2)–C(1) 1.314(6) 1.357 1.385 Ag(1)-N(4)-N(3)
N(3)–C(1) 1.390(6) 1.390 1.410 N(2)-Ag(1)-N(4)
N(4)–N(3) 1.273(5) 1.296 1.326
120.0(3) 118.597 122.609
111.7(2) 109.589 112.895
67.44(12) 68.006
64.667
≠ Theoretically generated structure using the DFT computational technique.

28
Table 3. 1H NMR spectral data of the complexes in CDCl3 at room temperature
t
bs
4-Hs
7.39
7.40
5-Hs
7.21
7.20
7,11- Hd 8,10- H 9-R
12-CH2 LCH3- (CH2)*-CH2-
Compound
7.71
(8.2)
7.76
(7.6)
7.71
7.47m
7.50m
2.44
4.55
(6.4)
4.57
(7.0)
4.62
1.40-1.10
1.42-1.23
[Ag(Haai-C4H9)2]ClO4 (11a)
[Ag(Meaai-C4H9)2]ClO4 (11b)
7.35
(7.0)
7.49m
7.41
7.44
7.22
7.22
7.58
2.40
1.43-1.12
1.42-1.23
[Ag(Haai-C6H13)2]ClO4 (12a)
[Ag(Meaai-C6H13)2]ClO4 (12b)
(8.2)
7.86
(6.4)
4.55
7.42
(7.6)
7.72
(8.1)
7.96
(7.9)
7.72
(8.1)
7.99
(7.8)
7.73
(7.0)
7.51m
(7.0)
4.61
(6.3)
4.58
(7.1)
4.60
(6.8)
4.53
(7.1)
4.59
7.46
7.43
7.47
7.44
7.22
7.21
7.20
7.21
7.59
2.42
7.59
2.45
1.45-1.10
1.43-1.02
1.46-1.03
1.45-1.03
[Ag(Haai-C8H17)2]ClO4 (13a)
[Ag(Meaai-C8H17)2]ClO4 (13b)
[Ag(Haai-C10H21)2]ClO4 (14a)
[Ag(Meaai-C10H21)2]ClO4 (14b)
7.41
(7.0)
7.52m
7.41
(7.4)
7.53m
7.48
7.42
7.23
7.22
7.58
2.47
1.48-1.24
1.47-1.24
[Ag (Haai-C12H25)2]ClO4 (15a)
[Ag(Meaai-C12H25)2]ClO4 (15b)
(8.5)
7.99
(7.4)
4.54
7.38
(8.7)
7.74
(8.1)
7.95
(7.9)
7.75
(7.8)
(7.0)
7.52m
(7.5)
4.58
(7.2)
4.52
(7.1)
4.57
(6.3)
7.41
7.42
7.44
7.25
7.20
7.23
7.59
2.46
7.61
1.49-1.04
1.48-1.1
[Ag(Haai-C14H29)2]ClO4 (16a)
[Ag(Meaai-C14H29)2]ClO4 (16b)
[Ag(Haai-C16H33)2]ClO4 (17a)
7.35
(7.4)
7.54 m
1.51-1.14

29
7.40
7.43
7.47
7.44
7.48
7.48
7.47
7.22
7.22
7.21
7.21
7.19
7.17
7.18
7.98
7.33
2.48
7.58
2.47
7.62
2.49
7.62
2.48
4.51
1.52-1.24
1.52-1.21
1.51-1.11
1.53-1.42
1.55-1.35
1.58-1.23
1.57-1.25
[Ag(Meaai-C16H33)2]ClO4 (17b)
[Ag(Haai-C18H37)2]ClO4 (18a)
[Ag(Meaai-C18H37)2]ClO4 (18b)
[Ag(Haai-C20H41)2]ClO4 (19a)
[Ag(Meaai-C20H41)2]ClO4 (19b)
[Ag(Haai-C22H45)2]ClO4 (20a)
[Ag(Meaai-C22H45)2]ClO4 (20b)
(8.0)
7.76
(7.4)
(6.9)
4.57
7.53 m
(7.8)
7.98
(7.1)
4.49
7.32
(8.1)
7.79
(7.0)
(6.8)
4.56
7.54 m
(7.3)
7.95
(6.9)
4.48
7.54
(7.8)
7.80
(7.4)
(7.3)
4.55
7.54 m
(8.3)
7.98
(6.3)
4.47
7.35
(7.4)
(8.2)
(6.6)
sSinglet;
dDoublet;
tTriplet;
bsBroad Singlet;
mMultiplet.