OMAR
Thermal analyses
drawn also to the [Ru(dpa)2](PF6)2 which was found
to have the highest ligand field (501 nm, 19960 cm–1).
This is expected with two tridentate ligands (dpa’s)
which form with ruthenium four chelate rings com-
pared with three rings formed by hzpy and/or aepy in
the former complexes (Scheme 1).
The thermal studies of the ruthenium complexes were
carried out using the thermogravimetric TG and the
differential thermogravimetric DTG. The thermal data
was represented by Fig. 1 while the temperature ranges
of decompositions along with the corresponding mass
loss of species for all steps are given in Table 3.
[Ru(hzpy)3](PF6)2 was thermally decomposed in
four successive decomposition steps within the tem-
perature range 50–1000°C. The first decomposition
step with an estimated mass loss of 2.36% (calc.
mass=17) within the temperature range 50–138°C,
may be attributed to the liberation of the NH3 mole-
cule. The second decomposition step found in the
range of 138–258°C with an estimated mass loss
of 5.30% (calc. mass=38) may be corresponded to the
removal of F2 molecule. The third decomposition step
found within the temperature range 258–617°C with an
estimated mass losses of 60.56% (calc. mass
losses 436) which is reasonably accounted for by the
decomposition of the organic ligands (hzpy’s) along
with part of the inorganic counter ion as PF5. The rest
of the inorganic counter ion is removed in the fourth
step as PF5 in a wider temperature range 617–990 with
a mass loss of 17.58% (calc. mass loss=126). Ruthe-
nium metal (Ru) was remained at the end of decompo-
sition as the metallic residue (14.06%; mass=101) [15].
[Ru(hzpy)2(aepy)](PF6)2 decomposed in five de-
composition steps within the temperature range
50–700°C. The first two decomposition steps are very
close (50–114, 114–138°C) with a total estimated
mass loss of 14.85% (calc. mass=109) may be attrib-
uted to the removal a hzpy ligand. The rest of the or-
ganic matter is removed in the third and the fourth de-
composition steps (138–314, 394–571°C) with mass
losses of 21.90 and 14.95% corresponding to
(aepy+F2) and hzpy, respectively. The inorganic mat-
ter is removed in the fifth step (571–700°C) as PF5
leaving ruthenium metal as the metallic residue (mass
remained=13.87%).
Diamagnetism of complexes
The magnetic moments of all complexes fell into zero
indicating the diamagnetic nature of these complexes.
The diamagnetism of the isolated ruthenium com-
plexes have been further confirmed from the 1H NMR
spectral measurements of [Ru(hzpy)(aepy)2](PF6)2
complex. The hzpy and aepy ligands displayed
multiplets at 8.62–7.23 with 4 protons (aepy, hzpy)
assigned for the aromatic protons of the pyridine ring,
Table 2. In addition, aminoethylpyridine (aepy)
showed two doublets at 3.14 ppm and 2.98 with an in-
tegration of 4 protons, assigned to the two CH2 pro-
tons. It displayed also singlet at 2.0 assigned to NH2
protons. The 2-hydrazinopyridine displayed two ad-
ditional singlets at 4.0 and 2.0 ppm with integration
corresponding to one and two protons which can be
assigned to NH and NH2 protons; respectively.
[Ru(hzpy)(aepy)2](PF6)2 complex showed multiplet
peaks in the range 6.8–9.5 ppm with integration
of 12 protons which may be assigned to the pyridine
ring protons. The complex showed also three peaks in
the range 3.4–4.3 ppm. The first singlet at 4.3 ppm
(1 proton) can be assigned to the NH proton of the
hzpy ligand while the other two multiplet peaks found
at 3.43–3.93 ppm (8 protons) may be assigned to the
four methylenes (CH2) of the two aepy ligands. The
peaks due to the three NH2 (with integration of 6 pro-
tons) were found in the range 1.03–1.93 ppm.
The diamagnetic nature of the complexes can be
explained in terms of the low spin d6 ruthenium(II)
complexes with t62g eg0 configuration [22].
[Ru(hzpy)(aepy)2](PF6)2 decomposed in three
well separated steps within the temperature range
276–990°C. The first decomposition step found in the
temperature range 276–480 with mass loss of 21.28%
(calc. mass=158.42) which may be assigned to the re-
moval of aepy ligand along with F2 gas. The second
decomposition step found in the temperature range
480–613°C with a mass loss of 48.02% is corre-
sponded to the removal of hzpy, aepy and part of the
inorganic matter as PF5. The rest of the associated
counter ion is removed in the fourth step (742–990°C,
mass loss 16.95%) as PF5 leaving ruthenium metal as
the metallic residue (mass remained 13.64%).
[Ru(dpa)2](PF6)2 decomposed in five decomposi-
tion steps within the temperature range of 50–926°C.
Fig. 1 TG and DTG curves of the thermal decomposition of
[Ru(hzpy(aepy)2](PF6)2 complex
610
J. Therm. Anal. Cal., 96, 2009