Electrical conductivity of chloro(phenyl)glyoxime and its Co(II), Ni(II) and Cu(II) complexes

Article abstract of DOI:10.1135/cccc20031233

Chloro(phenyl)glyoxime, a vicinal dioxime, and its Ni(II), Cu(II) and Co(II) complexes were prepared. XRD patterns of the complexes point to similar crystal structures. IR and elemental analysis data revealed the 1:2 metal-ligand ratio in the complexes. The Co(II) complex is a dihydrate. Temperature dependence of electrical conductivity of the solid ligand and its complexes was measured in the temperature range 25-250°C; it ranged between 10^-14-10^-6 Ω^-1 cm^-1 and increased with rising temperature. The activation energies were between 0.61-0.80 eV. The Co(II) complex has lower electric conductivity than the Ni(II) and Cu(II) complexes. This difference in the conductivity has been attributed to differences in the stability of the complexes.

Full text of DOI:10.1135/cccc20031233

Electrical Conductivity of Chloro(phenyl)glyoxime
1233
ELECTRICAL CONDUCTIVITY OF CHLORO(PHENYL)GLYOXIME AND
ITS Co(II), Ni(II) AND Cu (II) COMPLEXES
Orhan TURKOGLUa1,*, Mustafa SOYLAKa2 and Ibrahim BELENLIb
a
Department of Chemistry, Faculty of Arts and Sciences, Erciyes University, 38039 Kayseri,
1
2
Turkey; e-mail: turkoglu@erciyes.edu.tr, soylak@erciyes.edu.tr
Department of Physics, Faculty of Arts and Sciences, Erciyes University, 38039 Kayseri,
Turkey; e-mail: belenli@ibu.edu.tr
b
Received Jan uary 13, 2003
Accepted April 12, 2003
Ch loro(ph en yl)glyoxim e, a vicin al dioxim e, an d its Ni(II), Cu(II) an d Co(II) com plexes were
prepared. XRD pattern s of th e com plexes poin t to sim ilar crystal structures. IR an d elem en -
tal an alysis data revealed th e 1:2 m etal–ligan d ratio in th e com plexes. Th e Co(II) com plex is
a dih ydrate. Tem perature depen den ce of electrical con ductivity of th e solid ligan d an d its
–
14
–6
com plexes was m easured in th e tem perature ran ge 25–250 °C; it ran ged between 10 –10
–
1
–1
Ω
cm
an d in creased with risin g tem perature. Th e activation en ergies were between
0
.61–0.80 eV. Th e Co(II) com plex h as lower electric con ductivity th an th e Ni(II) an d Cu(II)
com plexes. Th is differen ce in th e con ductivity h as been attributed to differen ces in th e sta-
bility of th e com plexes.
Keyw ord s: Electrical con ductivity; Cobalt; Nickel; Copper; Ch loro(ph en yl)glyoxim e com -
plexes; Oxim es; Dioxim es; XRD.
Com plexes form ed by dim eth ylglyoxim e, vic-dioxim es an d related ligan ds
h ave been un der in ten sive in vestigation for a few decades. Research on
th ese m aterials h as gain ed m om en tum recen tly, due to th eir poten tial use
in trace-m etal an alysis, electroch em ical an d electro-optical sen sors, as cata-
lysts, an d in m edical application s1 . Vicin al dioxim es are am ph oteric, as
th ey h ave both acidic h ydroxy groups an d sligh tly basic n itrogen atom s,
an d form com plexes with m an y tran sition m etals such as Ni(II), Cu(II),
Zn (II), Pd(II) an d Co(II). In th e com poun ds, two vic-dioxim e m olecules co-
ordin ate to a m etal ion , in a sym m etrical or un sym m etrical fash ion . Metal
ion s often bin d to four N atom s, facilitatin g two extra h ydrogen bridge
bon din gs, an d form com plexes with square-plan ar, square-pyram idal or oc-
tah edral geom etries. Som e ligan ds, such as substituted am in oglyoxim e, re-
act with Co(II) to give octah edral com plexes th at h ave two addition al water
–6
Collect. Czech. Chem. Commun. (Vol. 68) (2003)
doi:10.1135/cccc20031233

1
234
Turkoglu, Soylak, Belenli:
m olecules boun d in th e axial position s. On th e oth er h an d, Ni(II) an d
3
,7–9
Cu(II) ion s form square-plan ar com plexes with th e sam e ligan ds
.
Electroch em ical properties of vicin al dioxim e–m etal com plexes in solu-
tion h ave been reported3 . To our kn owledge, electrical properties of th e
com plexes in th e solid state h ave n ot yet been publish ed. Herein we report
on th e syn th eses, ch aracterization an d solid-state th erm o-electric beh avior
of th e ch loro(ph en yl)glyoxim e an d its Co(II), Ni(II) an d Cu(II) com plexes.
,10
EXPERIMENTAL
All th e ch em icals used were of an alytical grade (99.9%, Merck) an d used as supplied. For th e
syn th esis of 2-(h ydroxyim in o)-1-ph en yleth an -1-on e (ison itrosoacetoph en on e), m etallic so-
dium (2.3 g) in absolute eth an ol (100 m l) was cooled to –10 °C. Next, butyl n itrite (11.7 m l)
was slowly added to th e EtOH solution (ca 30 m in ) upon con tin uous stirrin g. Th e m ixture
was stirred at –10 °C for an oth er 20 m in , followed by dropwise addition of acetoph en on e
(
12 m l). Th e stirrin g of th e m ixture was con tin ued at room tem perature for an oth er 30 m in .
After stan din g overn igh t, th e resultin g red solid was filtered off an d wash ed several tim es
with dieth yl eth er. Th e crude product was redissolved in a m in im um am oun t of water an d
th e solution was acidified with acetic acid (1–3 m l). Th e wh ite precipitate of th e product
was filtered off, wash ed twice with water, an d recrystallized in eth an ol–water (1:2).
In order to form ph en ylglyoxim e, ison itrosoacetoph en on e (3.11 g) was dissolved in EtOH
(
20 m l). CH COONa (3.20 g) an d NH OH·HCl (1.79 g) were dissolved in H O (10 m l) an d
3 2 2
th e solution was added to th e ison itrosoacetoph en on e solution . Th e m ixture was refluxed
upon stirrin g at 100–110 °C for 4 h . After two days, water (60 m l) was added an d th e m ix-
ture was left stan din g overn igh t. Th e product was filtered off, wash ed twice with water, an d
stored in a vacuum desiccator.
Ch loro(ph en yl)glyoxim e (L) was prepared from ph en ylglyoxim e. For th e syn th esis,
ph en ylglyoxim e (5 g) was groun d in an agate m ortar, followed by addition of en ough ch lo-
roform . Dry ch lorin e was passed th rough th e suspen sion exposed to UV radiation for 15–
2
0 m in . At th e en d of th e reaction , a wh ite product was obtain ed. Th en , air was passed
th rough th e m ixture for 30 m in to rem ove excess ch lorin e.
Th e solid com plexes of th e ligan d L were prepared by addin g (upon con tin uous stirrin g)
1
0
5–20 m l aqueous solution s of CoCl ·6H O (0.119 g, 0.5 m m ol), NiCl ·6H O (0.119 g,
2 2 2 2
.5 m m ol) or CuCl ·6H O (0.085 g, 0.5 m m ol) dropwise to 20 m l of alcoh olic solution s of
2
2
th e ligan d (0.198 g, 1 m m ol); pH of th e m ixtures was between 3 an d 4. For precipitation
of th e com plexes, pH was adjusted to 5.5–6 by dropwise addition of 1% NaOH aqueous solu-
tion . Th e m ixtures were stirred on a water bath at 50–60 °C for 30 m in an d in an ice bath
for an oth er 30 m in . Th e products were th en filtered off, wash ed several tim es with cold wa-
ter an d dieth yl eth er, an d dried in a vacuum desiccator. Elem en tal an alyses (C, H an d N)
were perform ed with a CHNS-932 (LECO) apparatus.
Elem en tal an alyses. Th e ligan d L: for C H ClN O (198.6) calculated: 48.40% C, 3.55% H,
8
7
2
2
1
4.11% N; foun d: 49.01% C, 3.97% H, 14.66% N. Th e cobalt com plex: for C16H16Cl CoN O
2 4 6
(
490.2) calculated: 39.22% C, 3.27% H, 11.43% N; foun d: 39.85% C, 3.31% H, 11.15% N.
Th e n ickel com plex: for C16H12Cl N NiO (453.9) calculated: 42.36% C, 2.67% H, 12.35% N;
2
4
4
foun d: 41.87% C, 2.82% H, 12.08% N. Th e copper com plex: for C16H12Cl CuN O (458.7)
2
4
4
calculated: 41.87% C, 2.63% H, 12.22% N; foun d: 41.95% C, 2.60% H, 12.51% N. Th e co-
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Electrical Conductivity of Chloro(phenyl)glyoxime
1235
balt, n ickel an d copper com plexes an d th e ligan d are dark brown , green -yellow, black an d
wh ite, respectively.
X-ray powder diffraction (XRD) data of th e com plexes an d ligan d L were recorded with a
Bruker AXS D8 advan ced diffractom eter, usin g graph ite m on och rom atized CuKα radiation
operated at 40 kV an d 40 m A. Th e bon din g of th e ligan d L in th e in vestigated com plexes
was exam in ed by FTIR spectroscopy with a Jasco 330 m odel spectrom eter. Th e recorded FTIR
spectra of th e com plexes (KBr pellets) were com pared with th at of un coordin ate L. Magn etic
m om en ts in th e solid state were m easured with a Gouy balan ce at room tem perature by th e
Faraday m eth od, usin g m ercuric tetrath iocyan atocobaltate(II) as a susceptibility stan dard.
Diam agn etic correction s were m ade from th e Pascal’s con stan ts. Electron ic absorption spec-
tra of th e com poun ds in DMSO solution s were recorded on a Hitach i Model 150-20 UV-VIS
double-beam spectroph otom eter.
Th e total electric con ductan ce (σ ) of th e syn th esized com plexes an d th e ligan d L were
T
m easured on sam ple pellets (d = 12 m m , th ickn ess ≈ 1m m ) m ade in a stain less h older un der
3
–2
ca 5 × 10 kg cm pressure. Disk-sh aped pellets were sin tered in air at 70–80 °C for 24 h .
Scan n in g electron m icroscopy (SEM) revealed th at th e degree of com paction in all cases
ran ged between 80 an d 95%. Silver electrodes were vacuum -deposited as four n arrow lin es
on th e flat surface of th e pellets by DC sputterin g tech n ique. Fin e silver wires were attach ed
to th e silver-deposited region s usin g h igh -con ductivity silver pain t. After m akin g th e
four-poin t con tacts, th e pellets were h eated in air at 70–80 °C for 5 h to m ake th e con tacts
stron ger to h an dle an d to reduce con tact resistan ce. Th e oh m ic ch aracter of th e con tacts
was ch ecked prior to each m easurem en t. Th e electric con ductivity was m easured in th e
ran ge between room tem perature an d ca 250 °C by four-probe arran gem en t. Poten tial differ-
en ce E was m easured from th e in n er two probes with a Keith ley digital m ultim eter; th e cur-
ren t i was m easured with a Keith ley digital electrom eter. If th e distan ces S between th e
probes are th e sam e an d th e ratio L/S is h igh er th an 2, wh ere L is th e distan ce between th e
en d probes an d th e sam ple edge, th e total electric con ductan ce (σ ) can be calculated usin g
T
1
1
Eq. (1)
.
1
i
σ T
=
(1)
2
πS E
Th e tem perature of th e sam ples durin g th ese m easurem en ts was determ in ed by placin g a
th erm ocouple at about 5 m m from th e sam ple. Tem perature in crem en ts between th e m ea-
surem en ts were kept sm all an d th e m easurem en ts of th e sam ples at each tem perature were
perform ed after th erm al equilibrium h ad been reach ed.
RESULTS AND DISCUSSION
Elem en tal an alyses an d oth er ph ysical data sh ow th at th e ligan d L reacts
with m etal ion s (M = Cu2 , Ni or Co ), producin g ch elate com plexes of
+
2+
2+
th e ML type. Th ese com plexes are in soluble in water an d in m ost com m on
2
organ ic solven ts such as eth an ol, m eth an ol, aceton e, ch loroform an d ben -
zen e, an d poorly soluble in DMF an d DMSO. Th e com plexes are air-stable
solids th at gradually decom pose, m elt an d volatilize in th e tem perature
ran ge of 250–340 °C. Accordin g to th e form ulae of th e com plexes, both
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

1
236
Turkoglu, Soylak, Belenli:
Cu(II) an d Ni(II) ion s exh ibit coordin ation n um ber 4, wh ereas Co(II) is
h exacoordin ate, h avin g two water m olecules in th e coordin ation sph ere.
Th e m ain in frared stretch in g m odes of th e free ligan d an d th e ML ch e-
2
lates are sh own in Table I. Th e data sh ow th at both ligan ds are biden tate,
an d th e m etal ion s bin d to two ligan d m olecules th rough n itrogen atom s.
–
1
Th e ligan d O–H stretch in g vibration s h ave been observed at 3300 cm . Th is
vibration was n ot observed in th e IR spectra of th e com plexes. Th e disap-
pearan ce of th is ban d is due to th e form ation of M–N an d h ydrogen bon ds.
–
1
Th e com plexes sh ow IR absorption ban ds aroun d 1650–1680 cm
for
stretch in g m odes H–O···H an d at about 500 cm –1 for M–N stretch . Th ese
n ew bon ds cause a sh ift of th e C=N stretch in g frequen cies of th e com plexes
to 1610–1620 cm com pared to that of uncoordinate L (1640 cm ). In th e
case of th e Co(II) com plex, th e axially boun d water m olecules can be iden -
–1
–1
–
1
tified by broad ν(OH) ban d aroun d 3400–3360 cm th at keeps its in ten sity
even after h eatin g th e com plex at 125 °C for 12 h .
Table I also gives th e room tem perature m agn etic m om en ts of th e pre-
7
pared com plexes. Th e m agn etic m om en t of th e d Co(II) ch elate (µeff
=
4
.26 µ ) is with in th e ran ge reported for h igh -spin octah edral Co(II) com -
B
1
2,13
9
plexes
. Th e square-plan ar geom etry for th e d Cu(II) ch elate is also con -
firm ed by its m agn etic m om en t (µeff = 1.85 µ ) wh ich falls with in th e ran ge
B
reported in th e literature. For th e Ni(II) ch elate, th e diam agn etic n ature
is observed, as expected for d -m etal ion s in a square-plan ar field12,13.
Th e suggested geom etries of th e com plexes are depicted in Fig. 1. Due to
th e asym m etry of th e ligan d, th e com plexes are expected to exist as cis- an d
trans-isom ers.
8
TABLE I
Measured m agn etic m om en ts an d IR stretch in g frequen cies (cm –1) of th e ligan d L an d its
com plexes
C–H
arom .)
Com poun d
µeff (µB)
O–H
C=N
N–O
965
H2O
–
O–H⋅⋅⋅O Oth ers
(
a
L
Dia
3300 3090–3000 1640
–
a,b,c
[
[
[
Co(L) (H O) ] 4.26
–
–
–
3050
3040
3030
1620
1610
1620
940 3400–3360 1680
2
2
2
a,b
a,b
Ni(L)2]
Dia
950
950
–
–
1670
1650
Cu(L)2]
1.85
a
ν(C–Cl) ban ds at 690–760cm –1. b ν(M–N) ban ds at ca 500 cm –1. c ν(M–O) ban ds at ca
–
1
6
00 cm
.
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Electrical Conductivity of Chloro(phenyl)glyoxime
1237
Th e UV-VIS spectrum of th e ligan d exh ibits a ban d at 266 n m th at can be
attributed to th e n →π* tran sition of th e oxim e group3,12. On ly on e ab-
sorption ban d is presen t in th e UV-VIS spectra of th e com plexes, at 260 n m
2
+
2+
2+
for Co , 264 n m for Ni an d 279 n m for Cu . Th ese spectral data are as-
sign ed to th e in traligan d tran sition . Lower-lyin g absorption ban ds due to
d→d tran sition s could n ot be observed due to th e poor solubility of th e
com plexes.
Figure 2 sh ows X-ray diffraction pattern s of th e ligan d L an d th e studied
com plexes at room tem perature. Th e first peak of th e ligan d is m issin g in
diffractogram s of th e com plexes, but th e latter sh ow extra peaks, absen t in
th e XRD pattern of th e ligan d. Th ese extra peaks prove th e coordin ation of
th e m etal ion s. Th ese XRD pattern s also in dicate th at th e ligan d an d com -
plexes are crystallin e, with various degrees of crystallin ity. In particular, th e
XRD pattern s of th e ligan d an d th e Co(II) com plex h ave h igh er backgroun d
in ten sity an d reduced sh arpn ess of th e peak profiles th an th e Cu(II) an d
Ni(II) com plexes, th us in dicatin g poorer crystallin ity. Broaden in g of th e
peak profiles for th e Co(II) com plex m ay be due to th e two water ligan ds.
Th e XRD pattern s of th e Cu(II) an d Ni(II) com plexes are very sim ilar but
th at of th e Co(II) com plex is sligh tly differen t, exh ibitin g som e extra peaks
an d sm all sh ifts in all peak position s toward h igh er an gles. Th e close XRD
pattern s for th e studied com plexes poin t to th eir sim ilar crystal structures.
N OH
Cl
N OH
L
H
M
H
H
M
H
O
N
O
N
O
N
O
N
Cl
Cl
N
O
N
O
Cl
Cl
N
O
N
O
cis-isomer
trans-isomer
M = Ni(II), Cu(II), Co(II)(H2O)2
FIG. 1
Proposed structure for ML2 com plexes
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

1
238
Turkoglu, Soylak, Belenli:
Despite m an y efforts, n o sin gle crystals of th e com plexes were obtain ed to
allow crystal structure determ in ation .
Table II sh ows activation en ergies an d pre-expon en tial factors for th e
ligan d L an d th e com plexes un der study. Activation en ergy is lowest for th e
Cu(II) com plex th at sh ows th e h igh est con ductivity, an d h igh est for th e
Co(II) com plex th at sh ows th e lowest con ductivity. Th e activation en ergy
values do n ot exh ibit large differen ces, in dicatin g sim ilar forbidden en ergy
gaps for th ese com poun ds. Low values of th e activation en ergy, despite
very low con ductivity, in dicate th at th e con duction is likely to occur via
TABLE II
Activation en ergies (E ) an d pre-expon en tial factors (σ ) for th e ligan d L an d its com plexes
a
o
Com poun d
Ea, eV
σo, Ω–1 cm –1
L
0.74
0.80
0.68
0.61
0.49
0.37
0.54
0.68
[
[
[
Co(L) (H O) ]
2
2
2
Ni(L)2]
Cu(L)2]
a
b
c
d
1
0
20
30
40
50
60
70
80
2
θ, deg
FIG. 2
XRD pattern s of Cu(II) (a), Ni(II) (b), Co(II) (c) com plexes of ch loro(ph en yl)glyoxim e (d).
Coun t rates are drawn with differen t offset values
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Electrical Conductivity of Chloro(phenyl)glyoxime
1239
tun n elin g or h oppin g of ch arge carriers between localized states. Electron s
th erm ally excited from upperm ost filled m olecular orbitals to th e lowest
un occupied m olecular orbitals are th en assum ed to tun n el to equivalen t
em pty levels of th e n eigh borin g m olecules, wh ereas th e positive h oles
m ove in th e opposite direction , as reported in th e literature for sim ilar sub-
7
,11,14–17
stan ces
. In th e literature, electric con ductivities of som e organ o-
m etallic an d polym eric com poun ds, lyin g in th e sam e ran ge as th ose for
our com plexes an d h avin g sim ilar activation en ergies, h ave been explain ed
by tun n elin g or h oppin g of ch arge carriers7,15,17.
–
1
Figure 3 sh ows th e typical Arrh en ius plots of log σ vs T for th e m ateri-
T
als. Th ese data h ave been obtain ed durin g repeated h eatin g run s at a con -
stan t rate in air. Electric con ductan ce of th e ligan d L at 37 °C is 7.2 ×
–
13
–1
–1
1
0
Ω
cm an d th at of its Co(II) com plex even lower at th e sam e tem -
–
14
–1
–1
perature, viz. 5.5 × 10
oth er h an d, sh ow m uch h igh er con ductan ces at 37 °C, viz. 5.0 × 10
an d 1.1 × 10
Ω
cm . Th e Ni(II) an d Cu(II) com plexes, on th e
–
12
–
10
–1
–1
Ω
cm , respectively. Th e ligan d h as a quite low con ductiv-
ity at room tem perature because of a very sm all n um ber of ch arge carriers.
Th e con ductivity in creases with risin g th e tem perature up to 150 °C. Th e
–
9
–1
–1
m axim um con ductan ce for th e ligan d was 1.25 × 10
Ω
cm at th is
tem perature, th is value bein g about four orders of m agn itude h igh er th an
its room -tem perature con ductan ce. Above 150 °C, th e ligan d started to m elt
an d decom pose. Th e n ature of th e electric con ductivity in th e sam ples is
electron ic.
–
–
–
5
7
9
–
11
–
–
13
15
1
.6
2.1
2.6
3.1
1/T) × 10 , K
3.6
3
–1
(
FIG. 3
Tem perature depen den ce of total con ductan ces (σ ) for ch loro(ph en yl)glyoxim e (L; ❏) an d its
T
com plexes [Co(L) (H O) ] (×), [Ni(L) ] (∆) an d [Cu(L) ] (❏)
2
2
2
2
2
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

1
240
Turkoglu, Soylak, Belenli:
In gen eral, th e total con ductan ce is given by σ = n |e| µ, wh ere n is th e
T
n um ber of ch arge carriers, e is th eir ch arge, an d µ is th eir m obility. As
sh own in Fig. 3, th e con ductan ce rises expon en tially with tem perature.
Tem perature depen den ce of th e observed electric con ductivity obeys th e
sim ple Arrh en ius equation (Eq. (2)):
σ T = σ exp (−E / kT),
(2)
o
a
wh ere σT is th e total electric con ductan ce, σo th e pre-expon en tial factor,
Ea th e activation en ergy, k Boltzm an n con stan t, an d T th e absolute tem per-
ature. It sh ould be n oted th at th e electric con ductivity m easured in th is
work is a bulk property in cludin g grain boun dary effects togeth er with in -
n er grain con ductivity. In trin sic con ductivity would be useful if sin gle crys-
tals of th ese com plexes were available; n everth eless, bulk con ductivities are
also n ecessary for un derstan din g electric con duction ph en om en a, bein g
valuable for com parison of com plexes.
With risin g tem perature, th e con ductivity in creases as a result of in creas-
in g ch arge carrier den sity due to th erm al activation . Th e m obility of th e
ch arge carriers is also tem perature-depen den t (proportion al to a power of
tem perature), but th e expon en tial tem perature depen den ce of th e ch arge
carrier den sity dom in ates th e th erm o-electric beh avior. In th e com plexes,
th e h ydrogen bon din g m ay play an in term ediary role in th e m ech an ism of
th e ch arge tran sfer between two ligan ds boun d to th e cen tral m etal ion ,
leadin g to en h an ced con ductivity with a decrease in activation en ergy. Th is
also in dicates th e possibility of som e degree of delocalization in th e excited
states.
Differen ces in th e con ductivity of th e com plexes m ay origin ate from dif-
feren t electron ic con figuration s of m etal ion s boun d to th e ligan d m ole-
cules. Th erm ogravim etric (TG) an d differen tial th erm al an alysis (DTA)
m easurem en ts h ave sh own th at th e decom position an d volatilization tem -
peratures of th e Co(II) com plex are h igh est an d th ose of Cu(II) com plex are
sligh tly lower th an for th e Ni(II) com plex. Th is suggests th at m olecular
bon din g an d h en ce stability differen ces am on g th e com plexes m ay lead to
differen ces in th eir ch arge carrier den sities an d/or m obilities. On th e oth er
h an d, differen t coordin ation geom etry of th e com plexes an d, h en ce, differ-
en t m olecular packin g an d in term olecular in teraction s are probably also re-
spon sible for differen ces in th eir electrical con ductivity. Th e con ductivity
of th e Co(II) com plex is lower th an th ose of th e oth er com plexes, in dicat-
Collect. Czech. Chem. Commun. (Vol. 68) (2003)

Electrical Conductivity of Chloro(phenyl)glyoxime
1241
in g its h igh er stability an d differen t geom etry (Fig. 1). Th e Cu(II) com -
poun d sh ows, on th e oth er h an d, th e h igh est con ductivity, wh ich m ay be
explain ed by a h igh er ch arge carrier den sity due to its square-plan ar geom e-
try an d lower stability. Th e Cu(II) ion in its com plex h as on e m ore valen ce
electron th an th e Ni(II) ion . Th is extra electron occupies th e d x
2
−y2
orbital
an d m ay take part in in term etallic in teraction s. Th ese in teraction s can be
1
5
expected to take place between adjacen t atom s .
CONCLUSION
Ch loro(ph en yl)glyoxim e reacts with m etal ion s (M = Cu2+, Ni2+ or Co2+),
producin g ch elate com plexes th at are in soluble in com m on organ ic sol-
ven ts, an d poorly soluble in DMF an d DMSO. Th e com plexes are air-stable
up to tem peratures 290–340 °C. Th e Cu(II) an d Ni(II) com plexes h ave
square-plan ar geom etry an d th e h igh -spin Co(II) com plex octah edral geom -
etry. XRD pattern s in dicate th at th e ligan d an d its com plexes h ave differen t
crystal system s with various degrees of crystallin ity. Th e th ree studied com -
plexes sh ow very close XRD pattern s, suggestin g sim ilar crystal structures.
Tem perature depen den ce of th e electric con ductivity of th e com plexes
obeys Arrh en ius equation with very low con ductan ce values. Electrical con -
ductivity in th e ligan d an d th e com plexes can be described by tun n elin g or
h oppin g of ch arge carriers between localized sites.
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