Synthesis, luminescence, and electrochemical studies of tetra- and octanuclear ruthenium(ii) complexes of tolylterpyridine appended calixarenes

Article abstract of DOI:10.1039/c6nj02564a

Tetra- and octanuclear Ru(ii) complexes of tolylterpyridine appended calixarenes, [{Ru(ttpy)}₄(L¹)](PF₆)₈ (3) and [{Ru(ttpy)}₈(L²)](PF₆)₁₆ (4) [L¹ = 5,11,17

Full text of DOI:10.1039/c6nj02564a

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PAPER
Synthesis, luminescence, and electrochemical studies of a tetra-
and an octanuclear ruthenium(II) complexes of tolylterpyridine
appended calixarenes†
Received 17th August 2016,
Accepted 00th xxxxx 20xx
Selvam Amudhan Senthan and Vedamanickam Alexander*
DOI: 10.1039/x0xx00000x
Tetra- and octanuclear Ru(II) complexes of tolylterpyridine appended calixarenes, [{Ru(ttpy)}4(L1)](PF6)8 (3) and
[{Ru(ttpy)}8(L2)](PF6)16 (4) [L1 = 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra(4′-p-benzyloxy-(2,2′:6′,2″-terpyridinyl))calix[4]-
www.rsc.org/
arene; L2
= 5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa(4′-p-benzyloxy-(2,2′:6′,2″-terpyridinyl))-
calix[8]arene; and ttpy = 4′-(p-tolyl)-2,2′:6′,2″-terpyridine] have been synthesized and characterized. 5,11,17,23-tetra-tert-
butyl-25,26,27,28-tetrahydroxycalix[4]arene (1) is characterized by single crystal X-ray diffraction, whereas
5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octahydroxycalix[8]arene (2) is characterized by NMR and
mass spectrometry. The tetra- and octanuclear complexes 3 and 4 are nonluminescent at 298 K, but exhibit 3MLCT
emission at 650 nm at 77 K in acetonitrile. In the solid state at 298 K they exhibit 3MLCT emission at 663 and 666 nm,
respectively. The polynuclear complexes 3 and 4 containing four- and eight [Ru(ttpy)2]2+ moieties undergo one-electron
oxidation at 1.27 and 1.25 V versus Ag/Ag+, respectively, in acetonitrile. The study demonstrates the versatility of the
tolylterpyridine appended calix[4]arene and calix[8]arene in forming polynuclear Ru(II) complexes.
Introduction
Calixarenes are attractive building blocks for a variety of
supramolecular architectures7 owing to their ability to bind neutral
With a myriad of organic and inorganic building blocks at their
disposal, chemists have been striving to design discrete molecular
hosts, similar to those found in nature,1 for applications in
chemistry and biology.2 Synthetic containers of nanoscale
dimension remain rare and the structures of biological shells
continue to inspire chemists towards the fabrication of nanoscale
molecular frameworks3 and the miniaturization of functional
microstructures.4 Selfassembly based on capsule components
bearing complementary functional groups capable of reversible,
noncovalent interactions such as hydrogen bonding and metal-
ligand interactions has yielded molecular5 and supramolecular
capsules2a capable of packing molecular guests. Encapsulation
places constraints on the translational motion of guest molecules6
and reversible encapsulation allows the temporary isolation and
characterization of guest molecules in small spaces. Although such
capsules are constructed with the express purpose of isolating
guest molecules from the bulk solvent, the medium must not
disrupt the interactions that hold the components of the capsule
together.
and cationic molecules inside their electron rich cavity and
simultaneously to form multiple hydrogen bonds with the hydroxy
groups. Appealing possibilities are offered by calixarenes which are
capable of both complexing small guest molecules and binding to
hydrogen bonding entities. In particular, functionalization of the
lower rim of calixarenes with suitable binding groups has produced
several cation receptors.7e,8 While the native calixarenes do not
generally possess significant solution affinity for organic molecules,
their binding ability may be enhanced markedly by elaboration of
the cavity. Calixarenes may also be transformed into effective
solution hosts by elaborating the upper rim. Calixarenes are used as
excellent three-dimensional anchors or molecular platforms to
append other binding groups through the O-alkylation of the lower
rim –OH functionalities.
The innate tunability of the excited-state properties of
transition metal complexes has been exemplified best by the
polypyridyl complexes of Ru(II), Os(II) and Re(I). Polypyridyl
complexes of these d6 metal ions, owing to their exceptional
spectroscopic and photophysical properties are promising
candidates for the construction of artificial photosynthetic devices,9
luminescent tags and probes,10 and molecular devices and
machines.11 Terpyridines and their structural analogs have gained
much interest as functional templates in the fields of
supramolecular and coordination chemistry and materials science.12
Due to their distinct photophysical, electrochemical, catalytic, and
magnetic properties, terpyridine-based metal complexes have been
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studied for
a
wide range of applications13 covering light-to- L1 and 10 equiv for L2) as the proton scavenger in dry DMF for L1
electricity conversion, light-emitting electrochemical cells, and tetrahydofuran for L2 under inert atmosphere.
electroluminescent systems and non-linear optical devices.
NMR spectra of ligands
Polynuclear arrays made up of the stereogenic [Ru(bpy)3]2+ motif
The NMR spectra of the tetra- and octanucleating ligands L1
gives rise to diastereomeric mixtures, whereas the achiral
[Ru(tpy)2]2+ motif forms stereopure assemblies. Thus, ruthenium(II)
complexes of terpyridine-based ligands are a good choice for the
construction of polynuclear assemblies.
and L2 show resonances corresponding to eleven and twenty
different proton and carbon environments, respectively. The signal
pattern indicates the presence of different electronic environments
for the tolylterpyridine groups, probably as a result of the slow
interconversion of the protons of the tolylterpyridine moieties on
the NMR timescale.
Supramolecular assemblies constructed by assembling
molecular components via covalent bonds greatly enhance the
possibilities to control the intramolecular intercomponent
interactions. This approach has been very helpful to the study of
photoinduced electron- and energy transfer processes14 and obtain
Synthesis of complexes
The tetra- and octanuclear complexes [{Ru(ttpy)}4(L1)](PF6)8 (3)
sophisticated functions such as stabilization of photoinduced charge and [{Ru(ttpy)}8(L2)](PF6)16 (4) are prepared by the reaction of the
separation,15 multielectron collection,16 harvesting of excitation preformed tetra- and octanucleating calixarene based ligands L1
energy in artificial antennas,17 and in various logical and switching and L2 (1 equiv) with [Ru(ttpy)Cl3] (4 equiv for 3 and 8 equiv for 4) in
functions.18 Calixarenes are excellent ligand frameworks for the refluxing ethylene glycol under inert atmosphere (Scheme 1). The
construction of polynuclear assemblies by covalently conjugating complexes are isolated in the solid state as hexafluorophosphate
multiple ruthenium(II)-based chromophores to the –OH salts.
functionalities at the lower rim. Polynuclear ruthenium(II)
Electronic absorption and luminescence spectra of complexes
complexes of tolylterpyridine appended calixarenes are expected to
The electronic absorption spectra of the tetra- and octanuclear
exhibit enhanced photophysical and redox properties. The
octanuclear [Ru(ttpy)2]2+ complexes appended onto the upper rim
ruthenium(II) complexes 3 and 4 feature ligand-centered (1LC) π−π*
transitions in the UV region and MLCT (dπ−π*) transition at 490 nm.
of the calixresorcarenes, reported by us, exhibit interesting
properties.19 Herein, we report the synthesis, luminescence and
The molar extinction coefficients of the electronic absorption bands
are roughly linearly dependent on the number of metal-based
electrochemical studies of tetra- and octanuclear Ru(II) complexes
chromophores. The electronic absorption spectra of the complexes
of tolylterpyridine appended calixarenes 3 and 4.
are presented in Figure 1 and the electronic absorption and
emission spectral data and the emission lifetimes are presented in
Table 1.
Results and discussion
Synthesis of calixarenes
8.0x105
5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]arene
(1) and 5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,
55,56-octahydroxycalix[8]arene (2) are synthesized by the base
induced condensation of 4-tert-butylphenol with formaldehyde in
refluxing phenyl ether and xylene, respectively. The mechanism of
the base-induced oligomerization of phenols and formaldehyde has
been discussed extensively.20 The p-substituent plays a significant
role in the formation of the cyclic tetramer and the methodology
employed in the synthesis of the octamer in the present study is
advantageous over earlier reported procedures in obtaining a single
product.
a
b
6.0x105
4.0x105
ε
ε
ε
ε
2.0x105
0.0
300
400
500
600
Wavelength (nm)
Crystal structure of calix[4]arene
Fig. 1 Electronic absorption spectra of (a) [{Ru(ttpy)}4(L1)](PF6)8 (3)
and (b) [{Ru(ttpy)}8(L2)](PF6)16 (4) in acetonitrile at room
temperature.
The X-ray crystal structure of 1 reveals that the molecule
possesses a rigid cone conformation and is isomorphous with that
of the earlier reported21 adduct of 1 with toluene (P4/n, a = b =
12.754(5) Å, c = 13.787(6) Å; α = β = γ = 90°). The crystallographic
data and ORTEP representation of 1 are presented in the electronic
supplementary information section.
The excitation spectrum of the free ligand L1 consists of bands at
272 and 312 (sh) nm and that of L2 contains bands at 258 (sh), 275
and 311 (sh) nm. The free ligand L1 emits at 342 (sh) and 353 nm
and L2 emits at 342 (sh) and 354 nm in fluid solution at room
temperature. The emission bands are independent of the excitation
wavelength. The complexes do not emit in solution at room
temperature, but they exhibit a Ru(II) centered emission band
originating from the 3MLCT state in the solid state at room
Synthesis of tolylterpyridine appended calixarenes
The tolylterpyridine functionalized tetra- and octanucleating
calixarenes L1 and L2 are synthesized by the O-alkylation of the
calix[4]arene (1) and calix[8]arene (2) (1 equiv) with 4′-(p-
bromomethylphenyl)-2,2′:6′,2″-terpyridine (ttpy-Br) (4 equiv for L1
and 8 equiv for L2) in the presence of cesium carbonate (5 equiv for
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1
L1
3
16+
16PF6
N
N
N
N
Ru
N
N
N
N
N
N
N
N
N
N
N
Ru
N
N
N
Br
N
N
N
N
Ru
N
O
O
N
N
N
N
N
N
N
Ru
Cl
N
O
O
O
O
N
N
N
N
OH
OH
Ru
N
N
OH
HO
Cl
Cl
N
N
N
N
N
OH
HO
O
O
O
O
N
Ru
a
b
N
N
OH
HO
N
N
N
O
O
O
O
N
N
N
N
N
N
N
O
O
N
Ru
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Ru
N
N
N
N
N
Ru
N
N
N
2
L2
4
Scheme 1 Synthesis of the polynuclear complexes [{Ru(ttpy)}4(L1)](PF6)8 (3) and [{Ru(ttpy)}8(L2)](PF6)16 (4): (a) Cs2CO3, DMF (L1) or THF (L2),
reflux, Ar, 36 h; (b) ethylene glycol, reflux, Ar, 8 h, KPF6.
Table 1 Photophysical and electrochemical data of the complexes
Complex
Entry Electronic absorption
Luminescencea λmax (nm)
E
b (V)
½
no.
banda (nm)
(ε × 104 dm3 mol-1 cm-1)
CH3CN, 293 K
Solid state, 293 K
CH3CN, 77 K
Metal centered Ligand centered
oxidation
1.27
reduction
−
−1.18, −1.40
[{Ru(ttpy)}4(L1)](PF6)8
[{Ru(ttpy)}8(L2)](PF6)16
[Ru(ttpy)2]2+c
3
284 (42.60)
309 (44.75)
490 (18.25)
284 (68.08)
310 (72.92)
490 (28.07)
490 (2.80)
663
650, 690
650, 690
628
−
4
666
1.25
1.24
−1.22, −1.44
−1.24,
−
−
−1.47
640
a Absorption and emission spectra were recorded using 10-6 M solution of the complexes in acetonitrile. b The data are computed from the cyclic
voltammograms recorded on a glassy carbon millielectrode in acetonitrile (10-3 M) using tetraethylammonium perchlorate as the supporting electrolyte (0.1
M) at 293 K at the scan rate of 50 mVs-1. Potentials are reported in volts versus Ag/Ag+. c Data taken from ref. 22.
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temperature at 663 nm and 666 nm and in frozen acetonitrile at 77 processes are, therefore, metal-centered, whereas the lowest
K at 650 and 690 nm, respectively. The emission maxima at 77 K are unoccupied molecular orbital (LUMO) are ligand-based and the
bathochromically shifted compared to that of the parent complex reduction processes are ligand centered.16d,22a,23 The single metal-
[Ru(ttpy)2]2+. The acute bite angle of the tridentate tolylterpyridine based redox process suggests that each ruthenium(II) chromophore
ligand activates the radiationless decay process through the 3MC is electronically “isolated” from the electrochemical viewpoint. The
states rendering the complexes non-emissive in fluid solution at cyclic voltammograms of the complexes are very similar suggesting
ambient temperature. The electronic absorption and luminescence that the calixarenes have little effect on the electronic environment
spectra of the polynuclear complexes 3 and 4 exhibit similar of the ruthenium(II) bis(tolylterpyridine) chromophores.
features suggesting minimal electronic interaction among the
tolylterpyridine units. Each [Ru(ttpy)2]2+ chromophore on the
Conclusions
periphery of the calixarenes is spectroscopically equivalent
indicating that the excited states are essentially localized on the
A
synthetic protocol has been established for incorporating
[RuII(ttpy)2] chromophores onto the calixarene frameworks. The
study demonstrates the versatility of calixarenes in the construction
of polynuclear ruthenium(II) complexes. The methodology
developed in the present work can be exploited to synthesize a
variety of polypyridine ligands appended calixarenes and their
polynuclear complexes. Further, the present work has a wide scope
of developing several polynuclear compounds of differing electronic
and geometric structures to assess how changes in such
characteristics are manifested in polynuclear assemblies. The high
nuclearity of the complexes does not affect their solubility in
organic solvents, a unique feature of calixarene-based compounds.
The temperature dependent Ru(II) emission confirms that the
thermally activated decay via the 3MC states is efficient in these
systems. The high molar absorption coefficients of the polynuclear
complexes due to the increase in the number of ruthenium
bis(tolylterpyridine) chromophores promises their use in light
harvesting study.
chromophore. The emission spectra of the complexes are depicted
in Figure 2.
a
1.0
b
0.8
0.6
0.4
0.2
0.0
550
600
650
700
750
800
850
Wavelength (nm)
1.0
0.8
0.6
0.4
0.2
0.0
a
b
Experimental
Materials
Acetamide, ammonium acetate, ammonium iron(II) sulfate
hexahydrate, N-bromosuccinimide, dibenzoyl peroxide, ethylene
glycol, formaldehyde solution (37%), hydrochloric acid (35%),
potassium hydroxide, silica gel (100-200 mesh) for column
chromatography, sodium hydroxide, and sodium sulfate
(anhydrous) (Merck); 2-acetylpyridine, cesium carbonate, phenyl
ether (99%), potassium hexafluorophosphate, ruthenium(III)
chloride trihydrate, 4-tert-butylphenol, p-tolualdehyde, and xylenes
(isomers) (98%) (Aldrich) were used as received. Acetone,
acetonitrile, carbon tetrachloride, chloroform, dichloromethane,
N,N-dimethylformamide, ethanol, and methanol were purified by
the standard procedures.24
600
650
700
750
800
850
Wavelength (nm)
Fig. 2 Emission spectra of (a) [{Ru(ttpy)}4(L1)](PF6)8 (3) and (b)
[{Ru(ttpy)}8(L2)](PF6)16 (4): (A) solid state at room temperature, (B)
acetonitrile at 77 K.
Physical measurements
Electrochemistry of complexes
CHN microanalyses were carried out using a Perkin–Elmer
2400 Series II CHNS/O Elemental Analyzer interfaced with a Perkin–
Elmer AD 6 Autobalance. Helium was used as the carrier gas.
Infrared spectra were recorded on a Perkin–Elmer Spectrum RX-I FT
IR spectrometer in the range 4000–400 cm−1 using KBr pellets. NMR
spectra were recorded on a Bruker AVANCE III 500 MHz (AV 500)
multinuclear NMR spectrometer working at 500 MHz at 25 °C. A
The redox behavior of the complexes has been investigated in
acetonitrile to complement the spectroscopic data. The cyclic
voltammetric data for the complexes 3 and 4 are presented in Table
1. The complexes undergo one metal-centered oxidation in the
positive potential window (0 to 1.5 V) and two successive ligand-
centered reductions in the negative potential window (0 to −2 V). In
ruthenium(II) polypyridyl complexes, the highest occupied
molecular orbital (HOMO) is metal-based and the oxidative
standard
5
mm probe was used for the 1H and 13C NMR
measurements. The electrospray ionization mass spectra (ESI MS)
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were performed using a Micromass Quattro-II Triple Quadrupole Synthesis of organic precursors
4′-(p-tolyl)-2,2′:6′,2″-terpyridine (ttpy),22b 4′-(p-bromomethyl-
phenyl)-2,2′:6′,2″-terpyridine (ttpy-Br),25 [Ru(ttpy)Cl3],26 and
5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]arene
(1)27 were synthesized by the literature methods.
mass spectrometer. The MALDI-TOF mass spectra were recorded on
a AB Sciex 4800 MALDI TOF/TOFTM instrument using the TOF/TOF
Series ExplorerTM software. 2,5-Dihydroxybenzoic acid or α-cyano-4-
hydroxycinnamic
acid,
dissolved
in
chloroform
and
acetonitrile/methanol, was used as the matrix.
5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-
The electronic absorption spectra were recorded on
a
octahydroxycalix[8]arene (2)
Shimadzu UV-2450 UV-Visible spectrophotometer controlled by the
UV Probe version-2.33 software. The spectra were recorded in the
region 190–900 nm in deaerated acetonitrile, chloroform, and N,N-
dimethylformamide at 25 °C using a matched pair of Teflon
stoppered quartz cell of path length 1 cm. Fluorescence spectra
were recorded on a Fluorolog-3 FL3-221 spectrofluorometer. The
excitation source was a 450 W CW Xenon lamp. The band pass for
the excitation and double-grating emission monochromator was set
at 2 nm. A quartz cell of path length 10 mm was used. The emission
spectra of the compounds were recorded in deaerated solvents.
Experiments at 77K in acetonitrile frozen glasses were carried out
using quartz capillary tubes immersed in liquid nitrogen contained
in a quartz dewar.
The compound 2 was synthesized by modifying the procedure
reported by Casnati et al.28 A mixture of p-tert-butylphenol (10 g,
66.57 mmol), formaldehyde solution (13.5 mL, 180.00 mmol), and
sodium hydroxide (1.10 g, 27.51 mmol) was heated under stirring at
100 °C for 2 h under nitrogen atmosphere in a round bottom flask
fitted with a Dean-Stark apparatus. Xylene (100 mL) was added to
the resulting yellow viscous substance and maintained between
100−110 °C unꢀl the reacꢀon mixture was free from water (~ 1 h)
and refluxed under nitrogen atmosphere for 6 h, and cooled to
room temperature. The solid compound that precipitated out was
filtered through a G4 filter funnel and washed with xylene (25 mL).
The solid product was stirred in a biphasic mixture of chloroform
(170 mL) and hydrochloric acid (0.1 M, 80 mL) for 20 min. The
organic layer was separated, washed thoroughly with water (3x100
mL), dried over anhydrous sodium sulfate (1 h), filtered,
concentrated to 50 mL, and hot acetone (100 mL) was added. The
white solid that separated out was filtered, dried in vacuo, and
recrystallized in chloroform. The compound was obtained as a
single product. White powder: (8.65 g, 80%), mp > 360 °C. Found: C,
81.37; H, 8.62. Calc. for C88H112O8: C, 81.44; H, 8.70. νmax/cm−1 3233
ν(O−H), 3053 νs(C−H) (aromaꢀc), 2957 νas(CH3), 2903 νas(CH2), 2868
νs(CH3), 1602, 1486, and 1452 νs(C=C) (aromatic), 1361 δs(CH3),
1203 ν(C−O), 1026, and 986 δs(C−H) (in-plane), 873, 815, and 783
γ(C−H) (aromaꢀc). δH(500 MHz; CDCl3; 298 K) 1.28 (72H, s, Ha), 3.52
(8H, d, J = 13 Hz, Hd), 4.39 (8H, d, J = 13 Hz, Hd), 7.20 (16H, s, Hb),
9.65 (8H, s, Hc). δC(125 MHz; CDCl3; 298 K) 29.7, 31.9, 34.0, 125.5,
128.7, 144.7, 146.6. MALDI-TOF MS: m/z 1319 [(M−H)+Na]+, 995
[(M+Na) − C22H28O2]+, 725 [(M+Na) − C40H50O4]+.
Cyclic voltammetry was performed on a EG&G PAR 273A
Potentiostat/Galvanostat using RDE0018 Analytical Cell Kit
consisting of a thermostated cell bottom, EG&G G0229 glassy
carbon disk millielectrode, platinum counter electrode, and EG&G
K0265 Ag/Ag+ reference electrode. The auxiliary electrode was
connected to the test solution through the counter electrode bridge
tube. The reference electrode was separated from the test solution
through the bridge tube containing AgCl–KCl filling solution. The
cyclic voltammograms were recorded using 10−3 M solution of the
complexes in oxygen free acetonitrile containing 0.1
M
tetraethylammonium perchlorate as the supporting electrolyte.
Oxygen free argon, saturated with the solvent vapor, was flushed
through each sample solution through the purge tube assembly for
30 min before voltammetry was performed and all measurements
were carried out in an atmosphere of argon at 25 °C. All operations
were performed through a computer using EG&G Model 270
Software and all electrochemical parameters were obtained using
Synthesis of tolylterpyridine appended calixarenes L1 and L2
the EG&G PowerSuite software. The instrument was calibrated by General Procedure. A solution of 1 or 2 (10 mmol) and cesium
recording the cyclic voltammograms of ferrocene (purum, Fluka) in carbonate (50 mmol for L1 and 100 mmol for L2) in dry DMF (2 L for
oxygen free acetonitrile under the same experimental conditions.
L1) or dry tetrahydrofuran (2 L for L2), taken in a two neck round-
bottom flask, fitted with a dropping funnel, was refluxed under
stirring for 1 h under argon atmosphere. A solution of 4′-(p-
bromomethylphenyl)-2,2′:6′,2″-terpyridine (40 mmol for L1 and 80
mmol for L2) in DMF (2 L for L1) or tetrahydrofuran (2 L for L2) was
added dropwise over a period of 1 h and refluxed under stirring for
36 h under argon atmosphere. The solution was flash evaporated to
dryness and the resulting solid product was dissolved in chloroform
(4 L) and washed with water (3x4 L). The organic layer was dried
over anhydrous sodium sulfate, filtered, and flash evaporated. The
resulting yellow solid was dried in vacuo and purified by silica gel
(100-200 mesh) column chromatography by eluting with
dichloromethane-hexane (7:3 v/v for L1 and 8:2 v/v for L2).
X-ray diffraction was carried out using a Bruker axs Kappa
ApexII single crystal X-ray diffractometer, equipped with graphite
monochromated Mo(Kα) (λ = 0.7107 Å) radiation and CCD detector.
The unit cell parameters were determined from 36 frames
measured (0.5° phi-scan) from three different crystallographic
zones using the method of difference vectors. The intensity data
were collected with an average four-fold redundancy per reflection
and optimum resolution (0.8 Å). The intensity data collection,
integration of frames, LP and decay corrections were done using
SAINT-NT (version 7.06a) software. Empirical absorption correction
(multiscan) was performed using SADABS (1999) program. The
structure was solved using SIR92 and refined using SHELXL-2014
programs. All non-hydrogen atoms were refined with anisotropic 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra(4′-p-benzyloxy-
displacement parameters. Hydrogen atoms were geometrically (2,2′:6′,2″-terpyridinyl))calix[4]arene (L1). Yellow powder: (38.40 g,
fixed at chemically meaningful positions and were allowed to ride 64%), mp = 200 °C (dec). Found: C, 80.76; H, 5.95; N, 8.57. Calc. for
over the parent atoms during refinement.
C132H116N12O4: C, 81.96; H, 6.04; N, 8.69. λmax(CHCl3)/nm 254 (ε/dm3
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mol−1cm−1 1 75 000), 279 (2 19 000) and 315 sh (52 750). νmax/cm−1
3052 νs(C−H) (aromaꢀc), 2954 νas(CH3), 2865 νs(CH3), 1602, 1584,
1567, 1467, and 1389 νs(C=C) and νs(C=N) (aromatic), 1122
νas(C−O−C), 790 γ(C−H), 739 δ(β-ring). δH(500 MHz; DMSO-d6; 298
K) 1.16 (36H, m, Ha), 2.05 (4H, s, Hc), 2.39 (4H, s, Hc), 4.62 (8H, s, Hd),
7.53 (8H, m, Hj), 7.89 (8H, d, J = 8.5 Hz, He), 8.02 (16H, m, Hb, Hi),
8.11 (8H, d, J = 9.5 Hz, Hf), 8.67 (8H, m, Hh), 8.70 (8H, s, Hg), 8.76
(8H, m, Hk). δC(125 MHz; DMSO-d6; 298 K) 22.7, 31.4, 34.1, 62.9,
118.2, 118.7, 121.4, 124.9, 127.1, 127.7, 128.2, 130.4, 130.8, 137.9,
143.5, 144.6, 148.7, 149.8, 155.5, 156.1. MALDI-TOF MS: m/z 1613
[M − ttpy]+, 1290 [M − 2ttpy]+, 971 [M − 3ttpy]+.
Acknowledgements
This research work was carried out with the financial support from
the Department of Biotechnology (DBT) and Science and
Engineering Research Board (SERB), Government of India, New
Delhi. We sincerely thank Dr. Babu Varghese, Sophisticated
Analytical Instrumentation Facility (SAIF), IIT-Madras, Chennai, for
his help in solving the crystal structure. Thanks are due to Dr. M. S.
Moni, SAIF, IIT-Madras, Chennai, for recording the NMR spectra.
We also thank SAIF, CDRI, Lucknow, for recording the mass spectra.
5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-
Notes and references
octa(4′-p-benzyloxy-(2,2′:6′,2″-terpyridinyl))calix[8]arene
(L2).
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Table of contents entry
Tetra- and octanuclear ruthenium(II) complexes of tolylterpyridine appended calixarenes are
synthesized and their luminescence and electrochemical properties are investigated.
(PF6)8
O
O
O
O
N
N
N
N
N
N
Ru
N
N
N
Ru
N
N
N
N
Ru
N
N
N
N
N
Ru
N
N
N
N
N
N