G. Maayan et al. / Polyhedron 64 (2013) 365–370
367
was added, the mixture was stirred for 1 h, the ice bath was re-
moved, and stirring was continued over night. The solvent was
evaporated and the residue was washed 4 times with 0.5 N citric
acid, extracted with CHCl3, dried over Na2SO4 and the solvent
was removed. The product was obtained as a slightly yellow solid
(600 mg, 88% yield). 1H NMR d = 8.7 (m, 2H), 8.6 (d, 1H), 8.25 (d,
1H), 7.8 (dt, 1H), 7.45 (dd, 2H), 7.4 (m, 5H, phenyl Hs), 7.34 (m,
1H), 7.1 (dd, 1H), 5.4 (s, 3H).
on 6073 reflections, goodness-of-fit (GOF)on F2 = 1.038, largest elec-
tron density = 0.914 e Åꢁ3
.
[Cu(I)(HQP)2](PF6): A solution of HQP (10 mg, 0.045 mmol) in
acetonitrile (0.5 ml) was treated with a solution of Cu(I)(CH3CN)4-
PF6 (8.4 mg, 0.0225 mmol) in acetonitrile (0.5 ml) and the mixture
was stirred under inert atmosphere (N2) for 30 min. Removal of the
solvent under vacuum afforded a dark solid (41 mg, 90% yield). ESI-
MS: m/z = 506.7. 1H NMR (CD3CN) d = 8.78 (bd, 1H), 8.75 (bd,1H),
8.6 (d, 1H), 8.45 (shoulder + d, OH + 1H), 8.2 (bt, 1H), 7.53–7.45
(bm, 3H), 7.2 (bd, 1H).
2-(20-pyridyl)-8-hydroxyquinoline(HQP): 8-Benzyloxy-2-(20-pyri-
dyl)-8-hydroxyquinoline (600 mg, 1.9 mmol) was dissolved in for-
mic acid (90 ml) and treated for 3 h with H2 at atmospheric
pressure using 10% Pd/C (300 mg) as catalyst. The reaction mixture
was filtered, the solvent was removed, and the residue was purified
by column chromatography on silica gel with 9% methanol in chlo-
roform as eluent. The product (385 mg, 90% yield) was obtained as
a slightly yellow solid. 1H NMR d = 8.84 (dd, 1H), 8.74 (dq, 1H), 8.64
(d, 1H), 8.45 (bs, OH), 8.39 (d, 1H), 7.9 (dt, 1H), 7.55-7.45 (m, 3H),
7.18 (dd, 1H). ESI-MS m/z = 222.7.
[Ni(III)(HQP)2](PF6): A solution of HQP (20 mg, 0.09 mmol) in
methanol (2 ml) was treated with Ni(II) acetate (11.2 mg,
0.045 mmol) and was stirred for 30 min at room temperature. An
orange solid precipitated after the addition of NH4PF6 (0.56 ml of
a 2.6 M aqueous solution). It was filtered, dried and collected
(43 mg, 86% yield). Crystals were obtained from methanol solution
at room temperature. ESI-MS: m/z = 500.2.
Crystal data: Cell dimensions of the 0.3 ꢀ 0.1 ꢀ 0.05 mm3 orange
ꢀ
plates, C28H18N4O2Ni + CH4O + PF6 + H2O: triclinic, P1 (No. 2),
a = 8.776(1),
b = 13.642(2),
c = 24.911(3) Å,
a = 75.974(8),
2.4. Preparation of the metal complexes
b = 114.660(6), c
= 80.208(2), from 20° of data, T = 120 K,
V = 2843.3(6) Å3, Z = 4, formula weight = 686.19, Dcalc = 1.603 mg/
[Co(III)(HQP)2](PF6): To a solution of HQP (20 mg, 0.09 mmol) in
methanol (2 ml) was added Co(II) acetate (11.2 mg, 0.045 mmol)
and the solution was stirred for 30 minutes. An aqueous solution
of NH4PF6 (0.56 ml) was added and a red solid precipitated. It
was filtered and dried in the air (38.4 mg, 0.076 mmol, 85% yield).
ESI-MS: m/z = 501.77. 1H NMR (CD3CN) d = 8.95 (d, 1H), 8.66 (d,
1H), 8.4 (dd, 1H), 8.1 (dt, 1H), 7.55 (t, 1H), 7.30 (d, 1H), 7.22-7.18
(m, 2H), 6.76 (d, 1H).
mm3, = 0.820 mmꢁ1 5616 reflections collected, 0 6 h 6 6,
l
ꢁ9 6 k 6 10, ꢁ18 6 l 6 19, frame scan width = 0.5°, scan speed 1°/
120 s, typical peak mosaicity = 0.45°, 2617 independent reflections
(Rint = 0.071). Idealized hydrogen atoms were placed and refined in
a
riding mode. 740 parameters with 230 restraints, final
R1 = 0.0957 (based on F2) for data with I > 2
r(I) and R1 = 0.1076 for
all data based on 2617 reflections, goodness-of-fit (GOF) on
F2 = 1.068, largest electron density = 1.388 e Åꢁ3
.
Co(II)(HQP)2: A solution of HQP (10 mg, 0.045 mmol) in metha-
nol (0.5 ml) was treated with a solution of Co(II) acetate (5.6 mg,
0.0225 mmol) in methanol (0.5 ml) and the mixture was stirred
at rt under inert atmosphere (N2) for 30 min. Removal of the sol-
vent in vacuum afforded a dark red solid (39.7 mg, 0.079 mmol,
88% yield). The complex was crystallized from a methanol solution
at room temperature, under inert atmosphere. ESI-MS: m/z = 501.7.
Crystal data: Cell dimensions of the 0.3 ꢀ 0.1 ꢀ 0.05 mm3 orange
3. Results and discussion
3.1. Synthesis of HQP–metal complexes and their characterization by
ESI-MS and UV–Vis
HQP was used for the preparation of complexes with four metal
ions namely Co(II), Cu(II), Cu(I) and Ni(II). In a typical synthetic
protocol, an equivalent of the metal salt was added to two equiva-
lents of the ligand in methanol or acetonitrile solution and stirred
for half an hour at room temperature in air or under nitrogen. An
immediate color change was observed after mixing which signified
the formation of the complex. Isolation of the complexes from the
colored solution was done in one of the following ways: (i) concen-
plates
C28H18N4O2Co + 3(CH4O): Monoclinic, P291/c (No. 14),
a = 13.899(2), b = 14.095(2), c = 15.907(1) Å, b = 114.660(6), from
20° of data, T = 120 K, V = 2832.1(5) Å3, Z = 4, Formula weight =
597.52, Dcalc = 1.401 Mg/m3,
l
= 0.653 mmꢁ1. 5106 reflections col-
lected, 0 6 h 6 13, 0 6 k 6 13, ꢁ15 6 l 6 13, frame scan width =
2.0°, scan speed 1°/180 s, typical peak mosaicity = 0.45°, 2525 inde-
pendent reflections (Rint = 0.062). Idealized hydrogen atoms were
placed and refined in a riding mode. 376 parameters with 0 re-
trated aqueous solution of NH4+PF6 was added, yielding the pre-
ꢁ
straints, final R1 = 0.0464 (based on F2) for data with I > 2
r
(I) and
R1 = 0.0609 for all data based on 2525 reflections, goodness-of-fit
(GOF) on F2 = 1.068, largest electron density = 0.509 e Åꢁ3
cipitation of the complex, which was filtered and collected, or (ii)
the solvent was removed in vacu to yield the solid complex.
All complexes were initially characterized by ESI-MS. As
depicted in Table 1, the m/z data clearly indicate that HQP forms
stable complexes of the type M(HQP)2 with all the metal ions. In
addition, data analysis of the complexes [Co(III)(HQP)2](PF6),
Co(II)(HQP)2, Cu(II)(HQP)2(PF6) and [Ni(III)(HQP)2](PF6) reflects
binding of each ion to two tridentate ligands (four nitrogens and
two oxygen atoms). An interesting observation is that the m/z of
the complexes [Cu(I)(HQP)2](PF6) and Cu(II)(HQP)2(PF6) differ by
two units, which is attributable to two protons on the two hydro-
xyl group on each of the two ligands. This observation suggests
that Cu(I) binds only to four coordinating atoms – the two nitrogen
atoms of each ligand [9]. A molecular peak of m/z = 144, indicative
of a PF6ꢁ anion, was also observed in this spectrum, indicating that
the Cu(I) ion is coordinated to four nitrogen atoms and do not
interact with the OH groups, and therefore its chꢁarge is neutralized
by an exterior hexafluorophosphate anion. PF6 peaks were also
observed in the spectra of all the other metal complexes, excluding
the spectrum of Co(II)(HQP)2. These results are discussed below
.
Cu(II)(HQP)2(PF6): A solution of HQP (20 mg, 0.09 mmol) in
methanol (2 ml) was treated with Cu(II) acetate (9 mg,
0.045 mmol) and was stirred for 30 min under inert atmosphere
(N2). An orange solid precipitated after the addition of NH4PF6
(0.56 ml of a 2.6 M aqueous solution). It was filtered, dried and col-
lected (40.9 mg, 90% yield). The complex was crystallized from
methylene chloride at room temperature. ESI-MS: m/z = 504.7.
Crystal data: Cell dimensions of the 0.2 ꢀ 0.1 ꢀ 0.05 mm3 orange
plates, 2(C28H18N4O2Cu) + 2(PF6) + 2(CH2Cl2): triclinic, P1 (No. 2),
a = 8.4690(4), b = 14.010(6), c = 25.9100(8) Å,
84.540(2), = 80.350(2), from 10° of data, T = 120 K,
V = 2925.5(2) Å3, Z = 4, formula weight = 735.9, Dcalc = 1.671 mg/
mm3, = 1.059 mmꢁ1
22,611 reflections collected, 0 6 h 6 8,
a = 75.180(2), b =
c
l
.
ꢁ13 6 k 6 13, -25 6 l 6 25, frame scan width = 1.0°, scan speed 1°/
60 s, typical peak mosaicity = 0.7°, 6073 independent reflections
(Rint = 0.043). 811 Parameters with 0 restraints, final R1 = 0.0639
(based on F2) for data with I > 2
r(I) and R1 = 0.0797 for all data based