P. Kondaiah, A. R. Chakravarty et al.
ACTHNUTRGNEUNG
Synthesis of [VO(L1)(phen)]·Cl (1) and [VO(L2)(L3)]·Cl (2): (HL1: Hsal-
Experimental Section
ambmz, HL2: Hsal-an-ambmz, L3: dppz-Gly-Gly-OMe): The complexes
were prepared by following a general synthetic procedure in which va-
nadyl sulphate (0.18 g, 1.0 mmol) dissolved in MeOH (15 mL) was treat-
ed with a solution of BaCl2 (0.24 g, 1.0 mmol). The mixture was stirred at
an ambient temperature for 2 h. BaSO4 thus precipitated was removed
from the reaction mixture using Celite. The blue-coloured filtrate was ini-
tially reacted with the Schiff-base ligand HL1 (0.25 g, 1.0 mmol) for com-
plex 1 and ligand HL2 (0.44 g, 1.0 mmol) for complex 2. The solution
colour changed to brown. The above solution was stirred for 45 min. The
phenanthroline base (1.0 mmol) was added (0.29 g phen for 1 or 0.45 g
dppz-Gly-Gly-OMe for 2) and the solution was stirred further for 2 h to
obtain a transparent yellow-brown solution. The resulting solution was
filtered and the filtrate was allowed to evaporate. The filtrate on concen-
tration gave a yellow solid on addition of diethyl ether. The solid was iso-
lated, washed with cold methanol, crystallized from methanol and finally
dried in vacuum over P4O10.
Materials and methods: All reagents and chemicals were purchased from
commercial sources (s.d. Fine Chemicals, India; Sigma–Aldrich, U.S.A.)
and used as such without further purifications. Solvents were purified by
standard procedures.[42] (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazo-
lium bromide (MTT) and propidium iodide (PI), N-acetyl cysteine
(NAC), and MitoTracker Deep Red FM (Cat. no.M22426) were pur-
chased from Sigma (U.S.A.) and Invitrogen BioServices India.
The elemental analysis was done using a Thermo Finnigan Flash EA
1112 CHNS analyzer. The infrared and electronic spectra were recorded
by using Bruker Alpha and PerkinElmer Spectrum 650 spectrophotome-
ters, respectively. IR spectra signals are assigned as follows: br, broad; vs,
very strong; s, strong; m, medium; w, weak. Emission spectral measure-
ments were carried out with a PerkinElmer LS 55 spectrophotometer.
Molar conductivity measurements were performed by using a Control
Dynamics (India) conductivity meter. Cyclic voltammetric measurements
were made at 258C on a EG&G PAR Model 253 VersaStat potentiostat/
galvanostat with an electrochemical analysis software 270 using a three
electrode set-up comprising a glassy carbon working electrode, a platinum
wire auxiliary, and a saturated calomel reference (SCE) electrode. Tetra-
butylammonium perchlorate (TBAP, 0.1m) was used as a supporting elec-
trolyte in DMF. The electrochemical data were uncorrected for junction
potentials. Electrospray ionization mass spectral measurements were per-
formed by using Esquire 3000 plus ESI (Bruker Daltonics) and Q-TOF
Mass spectrometers. Confocal microscopy experiments were performed
by using an Olympus 1X81 confocal electron microscope (Leica, TCS
SP5 DM6000). 1H NMR spectral measurements were made using
a Bruker 400 MHz NMR spectrometer. FACS Calibur (Becton Dickinson
(BD) cell analyzer) at FL1 channel was used in the biological study. Mag-
netic susceptibility measurement of the complex at 300 K was performed
with a powdered sample using MPMS SQUID VSM (Quantum Design,
USA). Preparation of HL1 and 9-bromomethyl anthracene was carried
out by literature methods.[22,43]
[VO(L1)
ACHTUNGTRENNUNG
at 258C; IR (KBr): n˜ =3364 (br), 3055 (w), 1614 (vs, C=N), 1539 (m),
1469 (w), 1414 (m), 1295 (m), 1199 (w), 1150 (w), 1047 (w), 960 (s, V=O),
908 (w), 850 (m), 723 (s), 616 (m), 431 (m), 574 cmꢀ1 (w); UV/Vis
(50% aq DMF): lmax (e): 693 (40), 400 (2460), 291 (15660), 272 nm
(33310 dm3 Mꢀ1 cmꢀ1); meff =1.64 mB; ESI-MS in MeOH: m/z 497.33 [M]+;
elemental analysis calcd (%) for C27H20ClN5O2V: C 60.86, H 3.78, N
13.14; found: C 60.64, H 3.63, N 13.06.
[VO(L2)(dppz-Gly-Gly-OMe)]·Cl (2): Yield: 0.64 g (ꢁ65%); LM
=
73 Sm2 Mꢀ1 in DMF at 258C; IR (KBr): n˜ =3277 (br), 3047 (w), 1739 (w),
1551 (m), 1614 (vs) (C=N), 1537 (s), 1492 (m). 1443 (m), 1405 (s), 1360
(w), 1290 (m),1029 (w), 964 (s) (V=O), 904 (w), 820 (w), 734 (vs), 619
(w), 562 (w), 420 cmꢀ1 (m); UV/Vis (50% aq DMF): lmax (e): 672 (90),
386 (17770), 370 (19360), 352 (14740), 291 sh (40490), 276 (66470),
256 nm (76390 dm3 mꢀ1 cmꢀ1); meff =1.63 mB; ESI-MS in MeOH: m/z
961.53 [M]+; elemental analysis calcd (%) for C54H40ClN9O6V: C 65.03,
H 4.04, N 12.64; found: C 64.89, H 4.17, N 12.60.
Solubility and stability: The complexes were soluble in MeOH, EtOH,
DMF and DMSO, moderately soluble in water; less soluble in MeCN,
CH2Cl2 and insoluble in hydrocarbons. They were stable in both solid
and solution phases.
Synthesis of dppz-Gly-Gly-OMe: tert-Butyloxycarbonyl (Boc)-protected
3,4-diaminobenzoic acid (1.0 g, 2.84 mmol) was treated with glycyl-gly-
cine methyl ester hydrochloride (0.83 g, 4.5 mmol) to form amide cou-
pling using N,N’-dicyclohexylcarbodiimide (DCC; 0.86 g, 4.2 mmol) in
15 mL of dry DMF. On subsequent deprotection of Boc, the reaction
mixture was treated with 1,10-phenanthroline dione (0.40 g, 1.9 mmol) to
isolate dppz-Gly-Gly-OMe in ꢁ50% yield as an off-white solid
(Scheme S1, the Supporting Information). 1H NMR (400 MHz,
[D6]DMSO): d=9.24 (dd, J1 =5.59 Hz, J2 =5.72 Hz, 1H), 9.16–9.10 (m,
3H), 9.06 (d, J=4.2 Hz, 1H), 8.76 (dd, J1 =5.73 Hz, J2 =5.85 Hz, 1H),
8.46 (s, 1H), 8.18 (d, J=8.74, 1H), 8.05 (d, J=8.81 Hz, 1H), 7.86–783 (m,
Time-dependent cathodic scan for 2 showed no apparent change in the
cathodic peak current (ipc) after 8 h indicating stability of the complex
(Figure S12e, the Supporting Information). The stability of 2 was also
studied by time-dependent UV/Visible spectroscopy in 1% DMSO in
DPBS buffer to maintain the cellular condition. The titration data
showed no apparent change in the spectral features even after 24 h. We
also checked the stability of complex 2 after and before 1 h photoirradia-
tion and the complexes were found to be stable (Figure S27, the Support-
ing Information).
1H), 7.80–7.77ACHTUNGTRENNUNG(m, 1H), 4.05 (d, J1 =5.69 Hz, 2H), 4.01 (d, J1 =5.84 Hz,
2H), 3.68 ppm (s, 3H); 13C NMR (100 MHz, [D6]DMSO): d=143.05,
141.97, 141.75, 141.42, 136.28, 133.74, 133.47, 131.01, 129.98, 129.85,
129.09, 127.97, 127.10, 125.16, 116.03, 55.01, 52.79, 43.41, 37.00 ppm; MS
(ESI+, MeOH): m/z 455.74 [M+H]+.
X-ray crystallographic procedures: The crystal structure of complex 1 as
its perchlorate salt (1a·EtOH) was obtained by using the single-crystal
X-ray diffraction method. Crystals were obtained on slow evaporation of
the ethanol/acetone solution of the complex in the presence of perchlo-
rate anion. Crystal mounting was done on glass fiber with epoxy cement.
All geometric and intensity data were collected at 228C using an auto-
mated Bruker SMART APEX CCD diffractometer equipped with a fine
focus 1.75 kW sealed tube MoKa X-ray source (l=0.71073 ꢂ) with in-
creasing w (width of 0.38 per frame) at a scan speed of 5 s per frame. In-
tensity data, collected using w–2q scan mode, were corrected for Lor-
entz-polarization effects and for absorption.[44] The structure was solved
by the combination of Patterson and Fourier techniques and refined by
full-matrix least-squares method by using the SHELX system of pro-
grams.[24] All hydrogen atoms belonging to the complex were in their cal-
culated positions and refined using a riding model. All non-hydrogen
atoms were refined anisotropically. CCDC-928547 (1a·EtOH), contains
the supplementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
parameters are given in Table 5.
Synthesis of HL2 (Hsal-an-ambmz): Boc-protected glycine (1.71 g,
9.7 mmol) was treated with phenylene diamine (1.05 g, 9.7 mmol) to pre-
pare the imidazole in ꢁ82% yield as an off-white solid. The anthracene
flurophore (1.64 g, 6.1 mmol) was attached to imidazole using NaH (60%
suspension in mineral oil) (0.71 g, 30.0 mmol) in 10 mL dry THF. Boc
was then deprotected to obtain the free amine, which was treated with
salicylaldehyde (221 mL, 2.1 mmol) to isolate the Schiff base in ꢁ75%
yield (0.68 g) (Scheme S1, the Supporting Information). 1H NMR
(400 MHz, CDCl3): d=12.48 (s, 1H), 8.47 (s, 1H), 8.09 (d, J=8.6 Hz,
2H), 7.98 (d, J=6.2 Hz, 3H), 7.74 (d, J=8 Hz, 1H), 7.41 (dd, 1J=4.2,
2J=4 Hz, 4H), 7.28 (dd, 1J=7.6, 2J=7.4 Hz, 1H), 7.18 (dd, 1J=7.4, 2J=
7.6 Hz, 1H), 7.02–6.99 (m, 2H), 6.92 (d, J=8.2, 1H), 6.84–6.76 (m, 2H),
6.30 (s, 2H), 4.84 ppm (s, 2H); 13C NMR (100 MHz, CDCl3): d=167.84,
161.09, 151.16, 142.92, 136.20, 133.19, 132.39, 131.71, 131.56, 130.31,
130.09, 127.94, 125.75, 124.56, 123.67, 123.43, 122.70, 120.46, 119.17,
118.97, 117.33, 111.09, 55.88, 42.38 ppm; MS (ESI+): m/z: 442.51
[M+H]+ in MeOH.
17452
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 17445 – 17455