Spectroscopic studies on charge-transfer complexes formed in the reaction of ferric(III) acetylacetonate with sigma- and pi-acceptors.

Article abstract of DOI:10.1016/j.saa.2003.08.018

The reaction of ferric(III) acetylacetonate (donor), Fe(acac)3, with iodine as a sigma-acceptor and with other different pi-acceptors have been studied spectrophotometrically at room temperature in chloroform. The pi-acceptors used in this investigation are 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), p-chloranil and 7,7',8,8'-tetracyanoquinodimethane (TCNQ). The results indicate the formation of 1:1 charge-transfer complexes with a general formula, [Fe(acac)3 (acceptors)]. The iodine complex was shown to contain the triiodide species, [Fe(acac)3]2I(+)I3-, based on the electronic absorptions as well as on the Far-infrared absorption bands characteristic for the non-linear triiodide species, I3-, with C2v symmetry. The proposed structure of this complex is further supported by thermal and middle infrared measurements.

Full text of DOI:10.1016/j.saa.2003.08.018

Spectrochimica Acta Part A 60 (2004) 1579–1586
Spectroscopic studies on charge-transfer complexes formed in the
reaction of ferric(III) acetylacetonate with ␴- and ␲-acceptors
S.M. Teleba, M.S. Refatb,∗
a
Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt
b
Chemistry Department, Faculty of Education, Suez Canal University, Port-Said, Egypt
Received 17 July 2003; accepted 19 August 2003
Abstract
The reaction of ferric(III) acetylacetonate (donor), Fe(acac)3, with iodine as a ␴-acceptor and with other different ␲-acceptors have been
studiedspectrophotometricallyatroomtemperatureinchloroform. The ␲-acceptorsusedinthisinvestigationare2,3-dichloro-5,6-dicyano-1,4-
benzoquinone (DDQ), p-chloranil and 7,7ꢀ,8,8ꢀ-tetracyanoquinodimethane (TCNQ). The results indicate the formation of 1:1 charge-transf−er
complexes with a general formula, [Fe(acac)3 (acceptors)]. The iodine complex was shown to contain the triiodide species, [Fe(acac)3]2I+I3
,
based on the electronic absorptions as well as on the Far-infrared absorption bands characteristic for the non-linear triiodide species, I3−, with
C2v symmetry. The proposed structure of this complex is further supported by thermal and middle infrared measurements.
© 2003 Elsevier B.V. All rights reserved.
Keywords: Charge-transfer; Far-infrared; Ferric(III) acetylacetonate; Triiodide; ␲-Acceptors
1. Introduction
One interesting aspect of the chemistry of metal acetylace-
tonates [M(acac)n] concerns the pseudo aromatic ␲-electron
delocalization in the M(acac) rings [16]. In all previous
studies [17–20] concerning the interaction of iodine with
metal acetylacetonates, it has been found out that the authors
who approached this topic have been ignored the formation
The study of the charge-transfer complexes formed in
the reaction of aromatic electron acceptors (␲-acceptors)
with various electron donors have attracted considerable in-
terests and growing importance owing to their significant
physical and chemical properties [1–6]. In previous studies
[7–12], it has been stated that iodine reacts with bases like
cyclic polyamines, polysulpher and mixed oxygen-nitrogen
to form stable charge-−transfer complexes with the formation
of polyiodide ions. In (n = 3, 5, 7, and 9).
−
of I3 with its characteristic absorptions around 290 and
360 nm. Remarkably, in their studies of the interaction of
iodine with metal acetylacetonates, Kulevsky and Butamina
[20], wrongly claimed that the 360 nm band was assigned
to the blue shifted I2 band, while the lower peak around
290 nm was attributed to the intermolecular charge-transfer
in M(acac)n–I2. In another study by Singh and Singh and
Sahai [17], the formation of a new absorption band around
360 nm was interpreted as a charge-transfer (CT) band of
the M(acac)n–I2 molecular complex.
In this paper, we report the formation of new CT-com-
plexes formed on the reaction of ferric(III) acetylacetonate,
Fe(acac)3, with different types of ␴- and ␲-electron accep-
tors. The ␴-acceptor used is iodine and the ␲-acceptors
are 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ),
tetrachloro-p-benzo-quione (p-chloranil) and 7,7ꢀ,8,8ꢀ-tetr-
acyanoquinodimethane (TCNQ). All reactions were carried
out in chloroform as a solvent. The obtained results enable
Some of charge-transfer complexes show very interest-
ing applications in the field of analytical chemistry [13,14].
Polyiodide charge-transfer complexes are of special interest
and importance. This is because some of these complexes
have shown interesting properties such as electrical conduc-
−
tivity. The highly conducting complex [(TTT)2]+I3 is re-
ported [15] to be formed in the reaction of iodine with the
sulphur containing base tetrathiotetracene (TTT).
∗
Corresponding author.
E-mail address: msrefat@yahoo.com (M.S. Refat).
1386-1425/$ – see front matter © 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2003.08.018

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S.M. Teleb, M.S. Refat / Spectrochimica Acta Part A 60 (2004) 1579–1586
Table 1
us to investigate the nature of bonding and structure inherent
in these new complexes.
The electronic absorption spectral data for (A) [Fe(acac)3]2I+I3; (B)
[Fe(acac)3(DDQ)]; (C) [Fe(acac)3(p-chloranil)]; and (D) [Fe(acac)3-
(TCNQ)] complexes, respectively in CHCl3
X ml of I2
Base:I2 ratio
Absorbance at 357 nm
2. Experimental
(A)
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
0.086
0.149
0.205
0.250
0.286
0.320
0.357
0.368
All chemicals used in this study were of analytical
reagent grade and used without further purification. Fer-
ric(III) acetylacetonate was obtained from Merck Chemi-
cal Co., while 2,3-dichloro-5,6-dicyano-1,4-benzoquinone,
tetrachloro-p-benzoquinone (p-chloranil) and 7,7ꢀ,8,8ꢀ-tetr-
acyanoquinodimethane was purchased from Aldrich
Chemical Co., and iodine was obtained from BDH.
X ml of DDQ
Base:DDQ ratio
Absorbance at 346 nm
The solid donor–acceptor complexes were isolated as
follows. Excess saturated solution for each of the ac-
ceptors in chloroform (40 ml) was added to a saturated
solution (10 ml) of the ferric(III) acetylacetonate in chlo-
roform. The mixture in each case was stirred for about
10–20 min. The brown [(Fe(acac)3]2I+I3−, dark brown
[Fe(acac)3(DDQ)], redish yellow [Fe(acac)3(p-chloranil)]
and greenish [Fe(acac)3(TCNQ)] solid CT-complexes
formed were filtered immediately and washed several times
with minimum amounts of chloroform (2–5 ml) and dried
under vacuum. The formed complexes were characterized
by their elemental analysis, vibrational and electronic ab-
sorption spectroscopy. The analysis data were obtained
as follows, [Fe(acac)3]2I+I3−: C, 29.31% (29.65%); H,
3.25% (3.46%); Fe, 8.98% (9.20%); I, 41.87% (41.80);
[Fe(acac)3(DDQ)]: C, 47.18% (47.57%); H, 3.39% (3.62%);
N, 4.75% (4.83); Cl, 11.97% (12.24%); Fe, 9.60% (9.63%);
[Fe(acac)3(p-chloranil)]: C, 41.93% (42.07%); H, 3.48%
(3.51%); Cl, 23.45% (23.70%); Fe, 9.17% (9.32%); and
[Fe(acac)3(TCNQ)]: C, 57.96% (58.13%); H, 4.40%
(4.49%); N, 9.89% (10.05%); Fe, 9.93% (10.02%) (the
calculated values are shown in parentheses).
The electronic absorption spectra of the donor [Fe(acac)3],
acceptors (iodine, DDQ, p-chloranil and TCNQ) and the
formed CT-complexes in chloroform were recorded in the
region of 700-200 nm using a Shimadzu UV-spectrophoto-
meter model 1601 PC with quartz cell of 1 cm path length.
The mid infrared spectra of the reactants and the formed
CT-complexes were recorded from KBr discs using a Gen-
esis II FT-IR, while the far-infrared spectra for the donor
[Fe(acac)3] and the iodine complex were recorded from Nu-
jol mulls dispersed on polyethylene windows in the region
50–300 cm−1 using a Mattson infinity series FT-IR spec-
trometer. Thermogravimetric (TG) and differential thermal
analysis (DTA) were carried out under N2-atmosphere us-
ing two detectors model Shimadzu TG-50 H and Shimadzu
DTA-50, respectively. Photometric titration were performed
[21] at 25 ◦C for the reactions of Fe(III) acetylacetonate
with the acceptors in chloroform as follow. The concentra-
tions of the donor [Fe(acac)3] in the reaction mixtures was
kept fixed at (1 × 10−4 M), while the concentrations of the
acceptors were changed over the range from 0.25 × 10−4
to 3.0 × 10−4 and these produced solutions with donor:
(B)
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
0.148
0.244
0.328
0.402
0.480
0.520
0.576
0.600
X ml of p-chloranil
Base:p-chloranil ratio
Absorbance at 353 nm
(C)
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
0.128
0.220
0.260
0.360
0.420
0.484
0.548
0.580
X ml of TCNQ
Base:TCNQ ratio
Absorbance at 408 nm
(D)
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
0.998
1.950
2.599
3.151
4.096
4.748
5.501
5.993
1 ml base (5 × 10−4 M) + X ml of (I2, DDQ, p-chloranil, and TCNQ)
(5 × 10−4 M) + Y ml solvent = 5 ml.
acceptor ratios varying from 1:0.25 to 1:3, as shown in
Table 1.
3. Results and discussion
The electronic absorption spectra of the reactants,
ferric(III) acetylacetonate, [Fe(acac)3], (1 × 10−4 M)
and acceptors (iodine, DDQ, p-chloranil and TCNQ)
(1×10−4 M) in CHCl3 along with those of the obtained 1:1
CT-complexes are shown in Fig. 1 (A–D, respectively). The

S.M. Teleb, M.S. Refat / Spectrochimica Acta Part A 60 (2004) 1579–1586
1581
Fig. 1. Electronic absorption spectra of: (A) [Fe(acac)3]–I2 re-
action in CHCl3; (B) [Fe(acac)3]–DDQ reaction in CHCl3; (C)
[Fe(acac)3]–p-chloranil reaction in CHCl3; and (D) [Fe(acac)3]–TCNQ
reaction in CHCl3. (a) Donor (1 × 10−4 M), (b) acceptor (1 × 10−4 M),
and (c) donor–acceptor CT-complex.
−
Fig. 2. Infrared spectra of: (a) [Fe(acac)3]2I+I3
complex; (b)
[Fe(acac)3(DDQ)] complex; (c) [Fe(acac)3(p-chloranil)] complex; and (d)
[Fe(acac)3(TCNQ)] complex.
spectra demonstrate that the formed CT-complexes have a
real strong absorption bands around 357 and 286 nm for
[(Fe(acac)3]2I+I3−, 346 and 268 nm for [Fe(acac)3(DDQ)],
353 and 290 nm for [Fe(acac)3(p-chloranil)] and at
408 nm for [Fe(acac)3(TCNQ)]. The stoichiometry of the
[Fe(acac)3(acceptor)] reactions were shown in all cases to be
of 1:1 ratio. This was proposed on the bases of the obtained
elemental analysis data of the isolated solid CT-complexes
as well as from the complexes infrared spectra, Fig. 2 and
Table 2, which indicate the existence of the bands charac-
teristic for both the [Fe(acac)3] and the acceptors. The stoi-
chiometry of 1:1 is also strongly supported by photometric
titration measurements. These measurements were based on
the CT absorption bands exhibited by the spectra for each of
the [Fe(acac)3(acceptor)] systems (indicated above) and are
given in Fig. 3. The Fe(acac)3(acceptors) equivalence points
indicate that the donor/acceptor ratio in all cases is 1:1 and
this result agrees quite well with the elemental analysis and
infrared spectra of the solid CT-complexes. Accordingly, the
formed CT-complexes upon the reaction of [Fe(acac)3] as
a donor with the ␴- and ␲-acceptors under investigation in
chloroform have the general formula [Fe(acac)3(acceptor)].
The 1:1 modified Benesi-Hildebrand equation [22], was
used to calculate the values of the equilibrium constant, K
(l mol−1) and the extinction coefficient, ε (l mol−1 cm−1).
Ca0Cd0l
Ca0 + Cd0
1
=
+
A
Kε
ε
where Ca0 and Cd0 are the initial concentrations of the accep-
tors (iodine, DDQ, p-chloranil and TCNQ) and the donor
[Fe(acac)3], respectively, while A is the absorbance of the
strong bands at 357 and 286 nm for [Fe(acac)3]2I+I3−, 346
and 268 nm for [Fe(acac)3(DDQ)], 353 and 290 nm for
[Fe(acac)3(p-chloranil)] and 408 nm for [Fe(acac)3(TCNQ)]
complexes. The data obtained throughout these calculations
are given in Table 3. Blotting the values of Ca0Cd0/A against
Ca0 + Cd0 values for each acceptor, a straight line is obtained
with a slope of 1/ε and intercept of 1/Kε as shown in Fig. 4.
The values of both K and ε associated with these complexes
are given in Table 4. These complexes show high values of
both the formation constant (K) and the extinction coeffi-
cients (ε). These high values of K confirm the expected high
stabilities of the formed CT-complexes as a result of the ex-
pected high donation of the ferric(III) acetylacetonate. The

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S.M. Teleb, M.S. Refat / Spectrochimica Acta Part A 60 (2004) 1579–1586
Table 2
Infrared frequenciesa (cm−1) and tentative assignments for DDQ, p-chloranil, TCNQ, [Fe(acac)3]2I+I3−, [Fe(acac)3(DDQ)], [Fe(acac)3(p-chloranil)], and
[Fe(acac)3(TCNQ)] complexes
−1
DDQ
p-Chloranil TCNQ
[Fe(acac)3]2I+I3
[Fe(acac)3(␲-acceptor)]
DDQ TCNQ
3441 s,br 3455 s,br 3455 s,br
Assignmentsb
p-Chloranil
3458 s,br
3347 vw
3250 w,br
–
3486 br
3292 ms
3406 w,br 3415 s,br
3236 sh
ν(O–H); H2O of KBr
3234 sh
3125 vw
3360 sh
–
3137 ms
3050 vs
2984 vw
2952 vw
2925 ms
2844 w
3005 w
2910 w
2866 vw
3005 w
3002 vw
2957 vw
2917 w
2830 vw
2202 s
3083 vw
3000 w
2958 vw
2930 w
2861 w
–
ν(C–H); Fe(acac)3 and TCNQ
2969 mw
2851 mw
ν(CH ); Fe(acac)3
3
–
–
–
2250 vw
2236 ms
1680 vs
1555 vs
1458 mw
1430 mw
2220 vs
–
2239 ms
2205 w
1665 vs
1566 vs
1519 vs
1444 w
1436 vw
ν(C N); DDQ and TCNQ
≡
1680 vs
1583 vs
1555 w,sh
1528 vw
1458 vw
–
1566 vs
1528 vs
1400 vw
1708 w
1569 vs
1525 vs
1416 vw
1690 s
ν(C O); Fe(acac)3, DDQ, and p-chloranil
=
ν(C C); Fe(acac)3, DDQ, p-chloranil, and TCNQ
=
1670 s
1539 vs
1572 vs
1530 vs
1416 vw
ν(C O); Fe(acac)3
=
δ(CH); Fe(acac)3
1389 vw
1250 s
1166 vs
1083 vw
1319 vw
1277 s
1236 ms
1194 vw
1097 vs
1352 s
1285 w
1205 w
1118 s
1044 w
1278 vs
1380 vs
1278 vs
1167 vs
1059 w
1020 vs
1377 vs
1345 sh
1266 vs
1178 s
1126 w
1029 vs
1375 vs
1278 vs
1250 vw
1190 ms
1115 vs
1025 vs
ν(C–C); Fe(acac)3, DDQ, p-chloranil and TCNQ
δ(CH ); Fe(acac)3
3
ν(C-CH ) + δ(CH), in-plane bend
3
1094 vw
1010 vs
δ(CH ), rock; Fe(acac)3
3
902 s
778 vs
986 vw
916 s
996 w
962 w
859 vs
808 w
930 s
884 vs
866 s
799 vs
930 vs
847 s
950 vs
792 w
ν(C-CH ) + ν(C–O); Fe(acac)3
3
CH-deformation; DDQ, p-chloranil and TCNQ
792 ms
708 s
764 s
722 s
772 vw
621 mw
775 vw
736 ms
765 s
750 s
766 s
δ(CH), out-of-plane bend + Ring
def. + ␯
+ δ(C-CH ) bend;
(M–O)
3
Fe(acac)3
611 mw
706 ms
688 vs
654 vs
710 ms
667 vs
655 s
569 s
ν(C–Cl); DDQ and p-chloranil CH,
in-plane bend; TCNQ skeletal
vibration
528 mw
458 mw
472 mw
430 vw
555 vw
472 vs
442 vs
425 ms
596 vs
542 vw
457 vs
416 ms
580 vs
446 vs
377 ms
570 vs
446 vs
390 s
Ring def. + ν(M–O); Fe(acac)3
CH, out-of-plane bend; TCNQ.
Skeletal vibration
a
s: strong; w: weak; m: medium; sh: shoulder; v: very; and br: broad.
ν: stretching; and δ: bending.
b
−
equilibrium constants are strongly dependent on the nature
of the used acceptor including the type of electron with-
drawing substituents to it such as cyano and halo groups.
The appearance of the two absorption bands around 360
and 285 nm are well known [23–25] to be characteristic for
the formation of the triiodide ion (I3−). This was also sup-
ported by the far-infrared spectrum of the iodine complex,
Table 5. This spectrum shows the characteristic bands for the
triiodide ion at 150, 102, and 76 cm−1, which are assigned
to νas (I–I), νs (I–I) and δ (I3−), respectively. These three
absorptions−do not exist in the spectrum of the donor. How-
ever, the I3 ion may be linear (D∞h) or non-linear (C2v).
Group theoretical analysis indicates that the I3 with C2v
symmetry displays three vibrations νs (I–I); A1, νas (I–I);
B2 and δ (I3−); A1, all are infrared active in good agree-
ment [23,26–29]−with the observed three infrared bands for
[Fe(acac)3]2I+I3 as shown in Table 5.
According to the foregoing discussion, a general mech-
anism is proposed for the formation of [Fe(acac)3]2I+I3
−
complexes as follows:
2[Fe(acac)3] + I2 → [Fe(acac)3]2I+I−
−
[Fe(acac)3]2I+I− + I2 → [Fe(acac)3]2I+I3

S.M. Teleb, M.S. Refat / Spectrochimica Acta Part A 60 (2004) 1579–1586
1583
Fig. 3. Photometric titration curves for the [Fe(acac)3]–acceptor reactions in CHCl3: (A) [Fe(acac)3]–iodine reaction at 357 nm; (B) [Fe(acac)3]–DDQ
reaction at 346 nm; (C) [Fe(acac)3]–p-chloranil reaction at 353 nm; and (D) [Fe(acac)3]–TCNQ reaction at 408 nm.
400 ◦C with a weight loss of 44.73% and may correspond
to the loss of 14C2H2 + 2CO2 + 5H2O + 2H2 molecules.
The calculated weight loss associated with the loss of these
species is 44.98% and agrees quite well with obtained value.
The weight found for the residue after decomposition is
13.97% giving an actual total weight loss of 86.03%. How-
ever, the calculated total weight loss (86.79%) supports our
conclusion about the thermal decomposition mode of the
complex, [Fe(acac)3]2I+I3−. Finally, the thermal decom-
position reactions of the complex can be summarized as
follows:
The formation of the iodine intermediate [Fe(acac)3]2I+I3
−
is well known to be formed between iodine and cyclic
polyamines [12,26]. To confirm the pr−oposed formula and
structure for the new [Fe(acac)3]2I+I3 complex, thermo-
gravimetric and differential thermal analysis were carried
out for this complex under N2 flow. DTA thermograms
and TGA curves are shown in Fig. 5. Table 6 gives the
maximum temperature values, Tmax (◦C), together with the
corresponding weight loss for each step of the decomposi-
tion reactions of this complex. The obtained data strongly
support the structure proposed for the iodine complex and
indicate that, the thermal decomposition of this complex
in inert atmosphere proceeds approximately with two main
degradation steps (Fig. 5). The first stage of degradation oc-
curs within a temperature range of 184–230 ◦C. The found
weight loss associated with this stage of decomposition is
41.3% and may be attributed to the loss of the two iodine
molecules, which is in good agreement with the calculated
value of 41.81%. The second stage of decomposition occurs
at a three different maximum temperature of 258, 372, and
−
+
=
[Fe(CH3COCH C(O)CH3)3]2I I3
164–222 ◦C
=
−−−−−→ 2[Fe(CH3COCH C(O)CH3)3] + 2I2
≥
=
2[Fe(CH3COCH C(O)CH3)3]2−→Fe2O3 + 14C2H2
+2CO2 + 5H2O + 2H2
The infrared spectra of the formed CT-complexes,
[Fe(acac)3(acceptor)] (acceptors: iodine, DDQ, p-chloranil,

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S.M. Teleb, M.S. Refat / Spectrochimica Acta Part A 60 (2004) 1579–1586
Table 3
The values Cd0+, Ca0, Cd0 +Ca0 and Cd0 +Ca0/A, for (A) [Fe(acac)3]2I+I3−; (B) [Fe(acac)3(DDQ)]; (C) [Fe(acac)3(p-chloranil)]; and (D) [Fe(acac)3(TCNQ)]
complexes, respectively, in CHCl3
Base:I2 ratio
Cd0 × 10−4
Ca0 × 10−4
Absorbance at 357 nm (Cd0 + Ca0) × 10−6
(Cd0Ca0) × 10−8
(Cd0Ca0/A) × 10−8 at 357 nm
(A)
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
0.086
0.149
0.205
0.250
0.286
0.320
0.357
0.368
125
150
175
200
250
300
350
400
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
2.90
3.35
3.65
4.00
5.25
6.25
7.00
8.15
Base:DDQ ratio
Absorbance at 346 nm
(Cdo · Cao/A) × 10−8 at 346 nm
(A)
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
0.148
0.244
0.328
0.402
0.480
0.520
0.576
0.600
125
150
175
200
250
300
350
400
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
1.689
2.049
2.287
2.488
3.125
3.846
4.340
5.000
Base:p-chloranil ratio
Absorbance at 353 nm
(Cdo · Cao/A) × 10−8 at 353 nm
(C)
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
0.128
0.220
0.260
0.360
0.420
0.484
0.548
0.580
125
150
175
200
250
300
350
400
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
1.953
2.273
2.885
2.778
3.571
4.132
4.562
5.172
Base:TCNQ ratio
Absorbance at 408 nm
(Cd0Ca0/A) × 10−8 at 408 nm
(D)
1:0.25
1:0.50
1:0.75
1:1.00
1:1.50
1:2.00
1:2.50
1:3.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
0.998
1.950
2.599
3.151
4.096
4.748
5.501
5.993
125
150
175
200
250
300
350
400
0.25
0.50
0.75
1.00
1.50
2.00
2.50
3.00
0.251
0.256
0.289
0.317
0.366
0.421
0.454
0.501
and TCNQ) are shown in Fig. 2, and their band assignments
are given in Table 2. These assignments are based on a com-
parison of the spectra of CT-complexes with those of the
reactants. The spectra of the reaction products contain the
Table 5
Fundamental vibrations for some triiodide compounds
Compounds
Assignmentsa
References
ν1
ν2
ν3
Table 4
Spectrophotometric results of CT-complexes of [Fe(acac)3]2I+·I3−,
[Fe(acac)3(DDQ)], [Fe(acac)3(p-chloranil)], and [Fe(acac)3(TCNQ)] in
CHCl3
KI3
CsI3
111
103
111
104
109
110
101
102
143
149
138
132
132
144
132
150
[23]
[27]
[27,28]
[28]
[26]
[26]
[29]
Present work
69
74
72, 66
60
61
(CH3)4NI3
(C2H5)4NI3
(TACPD)I+I3
(HMTACTD)I+I−3
[Ni(acac)2]2I+I3−
[Fe(acac)3]2I+I3
Acceptor
K (l mol−1
)
λmax (nm)
εmax (l mol−1 cm−1
)
−
−
I2
DDQ
p-Chloranil
TCNQ
4.222 × 104
4.273 × 104
4.167 × 104
0.760 × 104
357
346
353
408
0.526 × 104
0.851 × 104
0.800 × 104
10.526 × 104
84
76
a
ν1, νs (I–I); ν2, δ (I3−); ν3, νas (I–I).

S.M. Teleb, M.S. Refat / Spectrochimica Acta Part A 60 (2004) 1579–1586
1585
Fig. 4. The plot of (Ca0 × Cd0/A) values against (Ca0 + Cd0) values for the [Fe(acac)3]–acceptor reactions in CHCl3: (A) [Fe(acac)3]–iodine reaction at
357 nm; (B) [Fe(acac)3]–DDQ reaction at 346 nm; (C) [Fe(acac)3]–p-chloranil reaction at 353 nm; and (D) [Fe(acac)3]–TCNQ reaction at 408 nm.
−
−
Fig. 5. (A) DTA diagram of [Fe(acac)3]2I+I3 complex. (B) TGA diagram of [Fe(acac)3]2I+I3 complex.

1586
S.M. Teleb, M.S. Refat / Spectrochimica Acta Part A 60 (2004) 1579–1586
Fig. 5. (Continued ).
Table 6
[3] E.M. Nour, S.M. Metwally, M.A.F. El-Mosallamy, Y. Gameel, Spec-
trosc. Lett. 30 (1997) 1109.
[4] S.M. Metwally, Can. J. Appl. Spectrosc. 40 (6) (1995) 152.
[5] R. Foster, J. Chem. Soc. 1075 (1960).
The maximum temperature, Tmax (◦C), and weight loss values of the
decomposition stages for the [Fe(acac)3]2I+I3 complex
−
Decomposition Tmax (◦C)
Lost species
% weight losses
[6] K.K. Lahiri, K.K. Mazumdar, Spectrochim. Acta 46A (1990) 1137.
[7] M. Mizuno, J. Tanaka, I. Harada, J. Phys. Chem. 85 (1981) 1789.
[8] E.M. Nour, L.H. Chen, J. Laane, Raman J. Spectrosc. 17 (1986) 467.
[9] E.M. Nour, L.H. Chen, J. Laane, J. Phys. Chem. 90 (1986) 2841.
[10] E. Mulazzi, I. Pollini, L. Piseri, R. Tubino, Phys. Rev. B 24 (1981)
3555.
[11] E.M. Nour, Spectrochim. Acta 56A (2000) 167.
[12] E.M. Nour, L.A. Shahada, Spectrochim. Acta 44A (1988) 1277.
[13] L.I. Bebawy, K. El-Kelani, L. Abdel Fattah, A.S. Ahmed, J. Pharm.
Sci. 86 (9) (1997) 1030.
Found
Calculated
First stage
Second stage
212, 225 ◦C 2I2
41.30% 41.81%
44.73% 44.98%
≥365 ◦C
14C2H2 + 2CO2
+ 5H2O + 2H2
Total loss
Residue
86.03% 86.79%
13.97% 13.21%
[14] M. Luo, Yaowu Fenxi Zazhi 15 (6) (1995) 52.
[15] P.J. Trotter, P.A. White, Appl. Spectrosc. 32 (1978) 232.
[16] D.W. Thomson, Struct. Bonding 9 (1971) 27.
[17] P.R. Singh, R. Sahai, Aust. J. Chem. 23 (1970) 269.
[18] R. Sahai, V. Singh, J. Macromol. Sci. A22 (1985) 33.
[19] R. Sahai, V. Singh, R. Verma, J. Ind. Chem. Soc. 53 (1981) 670.
[20] N. Kulevsky, K.N. Butamina, Spectrochim. Acta 46A (1990) 79.
[21] D.A. Skoog, Principle of Instrumetal Analysis, third ed., Saunders,
New York, USA, 1985 (Chapter 7).
[22] R. Abu-Eittah, F. Al-Sugeir, Can. J. Chem. 54 (1976) 3705.
[23] W. Kiefer, H.J. Bernstein, Chem. Phys. Lett. 16 (1972) 5.
[24] L. Andrews, E.S. Prochaska, A. Loewenschuss, Inorg. Chem. 19
(1980) 463.
main bands for both the reactants, however, the bands of the
acceptors and [(Fe(acac)3] in the spectra of the complexes
show some changes in intensities and in some cases show
small shifts in the frequency values compared with those of
the free reactants. This could be understood in the basis of
symmetry and electronic structure changes in both acceptor
and [Fe(acac)3] in the formed CT-complexes compared with
those of the free molecules.
[25] K. Kaya, N. Mikami, Y. Udagawa, M. Ito, Chem. Phys. Lett. 16
(1972) 151.
References
[26] E.M. Nour, L.A. Shahada, Spectrochim. Acta 45A (1989) 1033.
[27] A.G. Maki, R. Forneris, Spectrochim. Acta 23A (1967) 867.
[28] F.W. Parrett, N.J. Taylor, J. Inorg. Nucl. Chem. 32 (1970) 2458.
[29] E.M. Nour, S.M. Teleb, M.A.F. El-Mosallamy, M.S. Refat, S. Afr.
J. Chem. 56 (2003) 10.
[1] R. Foster, Organic Charge-Transfer Complexes, Academic Press,
New York, 1969.
[2] R.S. Mulliken, W.B. Person, Molecular Complexes, A Lecture and
Reprint Volume, Wiley, New York, 1969.