Metal complexes derived from hydrazoneoxime ligands VI. Synthesis, characterization and structures of zinc(II) complexes derived from aroylhydrazoneoximes

Article abstract of DOI:10.1016/j.molstruc.2020.129571

The reaction of Zn(OAc)₂.2H₂O with substituted diacetylmonoxime aroylhydrazones H₂L-R, R = H, p-CH₃, p–OCH₃, p-Cland p-NO₂, using 1: 1 molar ratio, in acidified ethanol as a solvent afforde

Full text of DOI:10.1016/j.molstruc.2020.129571

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Metal complexes derived from Hydrazoneoxime Ligands VI.
Synthesis, characterization and structures of Zinc(II) complexes
derived from aroylhydrazoneoximes
Nahed M H Salem , Sabine Foro , Magdi F. Iskander
PII:
S0022-2860(20)31885-8
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.129571
MOLSTR 129571
To appear in:
Journal of Molecular Structure
Received date:
Revised date:
Accepted date:
22 July 2020
2 October 2020
31 October 2020
Please cite this article as: Nahed M H Salem , Sabine Foro , Magdi F. Iskander , Metal com-
plexes derived from Hydrazoneoxime Ligands VI. Synthesis, characterization and structures of
Zinc(II) complexes derived from aroylhydrazoneoximes, Journal of Molecular Structure (2020), doi:
https://doi.org/10.1016/j.molstruc.2020.129571
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1
Highlights
• Zn(II) complexes with diacetylmonoxime aroylhydrazones were
prepared.
• The molecular structure of the isolated complexes depends on the nature
of substituents in the aroylhydrazone ligands.
• Electron releasing substituents afforded dinuclear Zn(II) acetate
complexes.
• Electron attracting substituents gave either mononuclear or linear
polymeric chain Zn(II) acetate complexes.

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Metal complexes derived from Hydrazoneoxime Ligands VI. Synthesis,
characterization and structures of Zinc(II) complexes derived from
aroylhydrazoneoximes
Nahed M. H. Salem a, Sabine Forob , Magdi F. Iskander* a
a) Chemistry Department, Faculty of Science, Alexandria University, P.O. box 426,
Ibrahimia, Alexandria 21321, Egypt.
b) Material Science Department, Darmstadt Technical Univ., Alarich - Weiss str 4, 64287D
Darmstadt, Germany.
Corresponding author: Prof. Dr. Magdi F. Iskander, E-mail < m.iskander@link.net >
E-mail address for Dr. Nahed M. H. Salem < nahed_s@yahoo.com >
E-mail address for Sabine Foro < foro@tu.darmstadt.de >
Abstract
The reaction of Zn(OAc)2.2H2O with substituted diacetylmonoxime aroylhydrazones H2L-R,
R = H, p-CH3, p-OCH3, p-Cl and p-NO2, using 1 : 1 molar ratio, in acidified ethanol as a
solvent afforded [{Zn(HL-H)(OAc)}2].H2O 1, [{Zn(HL-CH3)(OAc)}2].H2O 2, [{Zn(HL-
OCH3)(OAc)}2].H2O 3, [Zn(HL-Cl)(OAc)(H2O)].H2O 4, [{Zn(HL-NO2)(OAc)}3]n 5
respectively. The isolated complexes were characterized by elemental analysis, IR spectra,
solution electronic absorption spectra, solution 1H NMR and 13C NMR spectra, and
electrospray ionization mass spectra ESI- MS. The crystal and molecular structures of 1, 2, 4
and 5 have been determined by single crystal x-ray diffraction. Self assembly and
supramolecular architectures of these complexes have been discussed. The substituent effects
of the aroylhydrazone residue on the binding modes of acetate anion as well as the nuclearity
and dimensionality of the formed complexes have been also discussed.
Key Words
Diacetylmonoxime aroylhydrazone, Zn(II) acetate complexes, Spectroscopy, X-ray crystal
Structures.

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1. Introduction
Multinuclear Zn(II) complexes have attracted attention for their structural diversity
[1 – 14] together with their applications as photoluminescence [15 – 21], electroluminescence
[22 – 23] and photoelectronic [24] materials. This class of Zn(II) complexes also finds
application in the field of catalysis [25 – 27] and photocatalysis [28] and is also involved in
the construction of metal – organic frameworks (MOFs) which can be used for gas adsorption
and storage [29 – 31]. Accordingly, varieties of binuclear [1 – 3], trinuclear [3 – 5],
tetranuclear [6 – 9] and polynuclear Zn(II) complexes [10 – 13] as well as Zn(II) polymers
[14] have been synthesized and characterized.
Multinuclear Zn(II) complexes derived from aroylhydrazones have been also reported
[1,6,28,32]. Aroylhydrazones ligands with appended potentially endogenous bridging groups
can link Zn(II) ions in closed or open multinuclear clusters [6]. Multinuclear Zn(II) acetate
aroylhydrazone complexes, where the acetate anion acts as bridging ligand have been
synthesized and structurally characterized [1,6,32]. Introducing oxime moiety to the
acyl/aroylhydrazone ligand e.g., diacetylmonoxime acyl/aroylhydrazones, resulted in the
formation diprotic NNO tridentate ligands (H2L) [33]. Both monomeric neutral bisligand
Zn(II) complexes [Zn(L)2] [33,34] and mixed ligand Zn(II) acetate complexes having
quinoline,
[Zn(HL)(CH3COO)(quin)].0.5
quin
[35],
and
imidazole
(HIm),
[Zn(HL)(CH3COO)(HIm)] [36],
coligands have been structurally characterized. To the
best of our knowledge, no multinuclear Zn(II) acetate complexes with diacetylmonoxime
acyl/aroylhydrazones have been reported. These findings and in continuation to our studies
on the coordination chemistry of Cu(II) and Ni(II) diacetylmonoxime acyl/aroylhydrazones
[37 – 40] prompt our interest to study Zn(II) acetate complexes derived from
diacetylmonoxime aroylhydrazones, aiming to clarify the effect of substituents of the

4
aroylhydrazone residue on the nuclearity and dimensionality of the obtained Zn(II) acetate
complexes.
2. Experimental
2.1 Materials
Zn(II) acetate dihydrate was of reagent grade quality and was used as received
without further purification. All solvents were distilled prior to use. Diacetylmonoxime was
obtained from Acros and used without purification. Aroylhydrazines were prepared by
hydrazinolysis of the corresponding methyl esters as previously described [41].
Aroylhydrazoneoxime ligands, H2L-R (R = H, CH3, CH3O, Cl and NO2), Scheme 1, were
prepared by the condensation of diacetylmonoxime with the corresponding aroylhydrazine in
methanol as previously described [40].
2.2 Synthesis of Zn(II) acetate complexes
To a solution of aroylhydrazonemonoxime, H2L-R ( R = H, CH3, CH3O, Cl, NO2) (1.0 mmol)
in ethanol (30 ml), a solution of zinc(II) acetate dihydrate (1.0 mmol, 0.2195 g) in ethanol (20
ml) was added. The resulting mixture was acidified with few drops of acetic acid and then
heated with constant stirring for 1 hr. The solution was then allowed to stand undisturbed for
few days until yellow crystals of the Zn(II) acetate complex were formed, then filtered off
and dried, at room temperature, under vacuum.
2.2.1 [{Zn(HL-H)(OAc)}2].H2O 1: Anal. Calc. for C26H32N6O9Zn2: C, 44.40; H, 4.59; N,
11.95. Found: C, 44.99; H, 4.89; N, 12.07%. IR(KBr) (cm-1): 3390 lattice water (O–H),
3155 hydrogen bonded oxime (O–H), 1610 (C=N–N=C), 1580, 1628, (OCO)asym., 1535
(C=N)ox, 1468, 1385 (OCO)sym, 1030 (N–O). UV–Vis (EtOH, max/nm (log): 240
1
(4.30), 350 (4.43), 380 sh. H NMR (DMSO-d6, ppm): 1.92 (6H, CH3COO), 2.09, 2.14 (6H,
CH3–C=NOH), 2.36, 2.37 (6H, CH3–C=NN), 7.42 (6H, aromatic), 8.11, 8.12 (4H, aromatic),

5
13
10.73 (2H, H2O), 11.73, 13.52 (2H, oxime O–H). C{1H} NMR (DMSO-d6, ppm): 10.57,
11.38 (CH3-C=N-OH), 13.50, 13.77 (CH3-C=NN) , 22.90 (CH3COO), 127.51, 127.68,
127.87, 129.78, 130.47, 136.18, 136.98 (CH-aromatic), 147.34, 148.23 (C=N-OH), 149.96,
150.91 (C=NN),
171.84, 172.61 (C6H5-CO),
176.58 (CH3COO). (+)ESI – MS
(DMF/CH3OH) m/z Calcd. (RA): 216.1 (216.5290) (1.5) [Zn(OAc)2(CH3OH)]; 256.7
(257.5813) (2.0) [Zn(OAc)2(DMF) + H+]1+; 283.1 (283.6247) (14.2) [Zn(HL-H)]1+; 343.5
(343.6771) (3.7) [Zn((HL-H)(OAc) + H+]1+; 355.8 (356.7191) (14.5) [Zn(HL-H)(DMF)]1+;
417.5 (416.7715) (3.7) [Zn(HL-H)(OAc)(DMF) + H+]1+; 429.6 (429.8136) (2.5) [Zn(HL-
H)(DMF)2]1+; 501.1 (502.8673) (17.2) [Zn(HL-H)2 + H]1+; 583.1 (584.2567) (33.6) [{Zn(L-
H)}2(H2O) + H]1+; 625.1(626.2939) (37.3) [{Zn(HL-H)}2(OAc)]1+; 638.2 (639.3359) (100)
[{Zn(L-H)}2(DMF) + H]1+; 711.2 (712.4304) (34.3) [{Zn(L-H)}2(DMF)2 + H]1+; 761.7
(759.4408) (7.6) [{Zn(HL-H)(OAc)}2(DMF) + H]1+; 848.2 (848.8584) (42.3) [{Zn(L-H)}3 +
H]1+; 921.2 (921.9527) (25.6) [{Zn(L-H)3(DMF)} + H]1+; 1129.1 (1131.4751) (35.8) [{Zn(L-
H)}4 + H]1+.
2.2.2 [{Zn(HL-CH3)(OAc)}2].H2O 2: Anal. Calc. for C28H36N6O9Zn2: C, 45.98; H, 4.96; N,
11.49. Found: C, 46.55; H, 5.17; N, 11.34%. IR(KBr) (cm-1): 3390 lattice water (O–H),
3160 oxime (O–H), 1630, 1580 (OCO)asym., 1612 (C=N-N=C), 1530 (C=N)ox, 1460,
1380 (OCO)sym, 1025 (N–O). UV–Vis (EtOH, max/nm (log): 252(4.26), 357 (4.42), 388
1
sh. H NMR (DMSO-d6, ppm): 1.93 (6H, CH3COO), 2.05, 2.12 (6H, CH3–C=NOH), 2.36
(6H p-CH3-C6H4), 2.36, 2.38 (6H, CH3–C=NN), 7.20, 7.22 (4H, aromatic), 8.01, 8.02 (4H,
aromatic), 11.60, 13.36, (2H, oxime O–H). 13C{1H} NMR (DMSO-d6, ppm): 10.59, 11.31
(CH3-C=NOH), 13.45, 13.74 (CH3-C=NN), 18.51, 21.02 (p-CH3C6H4), 23.15 (CH3COO),
127.56, 127.77, 128.29, 128.50, 133.45, 134.20, 139.32, 140.30 (CH-aromatic), 147.34,
148.23 (C=NOH), 149.45, 150.00 (C=NN), 170.10, 172.50 (C6H5-CO), 177.19 (CH3COO).
(+) ESI – MS (DMF/CH3OH) m/z Calcd. (RA): 257.2 (257.5813) (3.70) [Zn(OAc)2(DMF) +

6
H+]; 329.0 (329.6935) (1.7) [Zn(HL-CH3)(CH3OH)]1+; 357.2 (357.7039) (2.0) [Zn(HL-
CH3)(OAc) + H+]; 369.2 (370.7459) (10.3) [Zn(HL-CH3)(DMF)]1+; 430.2 (430.7983) (2.0)
[Zn(HL-CH3)(DMF) + H+]1+; 443.2 (443.8404) (5.0) [Zn(HL-CH3)(DMF)2]1+; 503
(503.8927) (8.0) [Zn(HL-CH3)(OAc))DMF)2 + H+]; 529.3 (530.9210) (10.3) [Zn(HL-
CH3)2 + H+]; 594.2 (594.2952) (36.8) [{Zn(L-CH3)}2 + H+]; 612.2 (612.3104) (25.3)
[{Zn(L-CH3)}2(H2O) + H]1+; 654.2 (654.3476) (13.2) [{Zn(HL-CH3)}2(OAc)]1+; 668.2
(667.3896) (100.0) [{Zn(L-CH3)}2(DMF) + H]1+; 740.53 (740.4840) (20.7) [{Zn(L-
CH3)}2(DMF)2 + H+]1+; 787.2 (787.4943) (8.8) [{Zn(HL-CH3)(OAc)}2(DMF) + H]1+; 890.2
(890.9387) (19.2) [{Zn(L-CH3)}3 + H]1+; 963.3 (964.0331) (34.1) [(ZnL-CH3)3(DMF) + H]1+;
1187.2 (1187.5824) (48.8) [{Zn(L-CH3)}4 + H]1+; 1298.4 (1298.7671) (35.8).
2.2.3 [{Zn(HL-CH3O)(OAc)}2].H2O 3: Anal. Calc. for C28H36N6O11Zn2: C, 44.06; H, 4.75;
N, 11.00. Found: C, 44.87; H, 4.73; N, 10.39%. IR(KBr) (cm-1): 3400 lattice water (O–H),
3158 oxime (O–H), 1628, 1585 (OCO)asym., 1610 (C=N-N=C), 1530 (C=N)ox, 1470,
1387 (OCO)sym, 1028 (N–O). UV–Vis (EtOH, max/nm (log): 265 (4.21), 360 (4.47), 395
1
sh. H NMR (DMSO-d6, ppm): 1.900, (6H, CH3COO), 1.973, 2.125 (6H, CH3–C=NOH),
2.338, 2.351 (6H, CH3–C=NN), 3.814 (6H, OCH3), 6.957, 6.971, 6.977 (4H, aromatic),
8.047, 8.064 (4H, aromatic), 10.65, (2H, O–H), 11.75, 13.36 (2H,oxime O–H). 13C{1H}
NMR (DMSO-d6, ppm): 10.59, 11.33 (CH3-C=N-OH), 13.38, 13.68 (CH3-C=NN), 22.53
(CH3COO), 56.02 (p-CH3OC6H4), 112.96, 113.21, 129.14, 129.46 (CH-aromatic), 147.55,
148.20 (C=N-OH),
149.45, 150.00 (C=NN), 170.10, 172.51 (C6H5-CO), 175.76
(CH3COO). (+) ESI – MS (DMF/CH3OH) m/z Calcd. (RA): 216.2 (216.5290) (6.0)
[Zn(OAc)2(CH3OH) + H+]1+; 248 (248.5710) (2.0) [Zn(OAc)2(CH3OH)2 + H+]1+; 257.3
(257.5813) (1.6) [Zn(OAc)2(DMF) + H+]1+; 312.7 (3.13.6510) (4.8) [Zn(HL-OCH3)]1+; 330.2
(330.6757) (6.0) [Zn(OAc)2(DMF)2 + H+]1+; 372.5 (373.7034) (6.0) [Zn(HL-CH3O)(OAc) +

7
H]1+; 386.2 (386.7453) [Zn(HL-CH3O)(DMF)]1+; 446.2 (446.7977) (2.0) [Zn(HL-
CH3O)(OAc)(DMF) + H+]1+; 459.2 (459.8397) (4.8) [Zn(HL-CH3O)(DMF)2]1+; 519.5
(519.8920) (4.5) [Zn(HL-CH3O)(OAc) (DMF)2 + H+]1+; 645.1 (644.3104) (100) [{Zn(L-
CH3O)}2 + (H2O) + H+]1+; 685.1 (686.3464) (6.2) [{Zn(HL-CH3O)}2(OAc)]1+; 698.2
(699.3883) (20.8) [{Zn(L-CH3O)}2(DMF) + H+]1+; 772.2 (772.4828) (11.5) [{Zn(L-
CH3O)}2(DMF)2 + H+]1+; 769.0 (769.3886) (10.4) [{Zn(HL-CH3O)(OAc)}2 + Na]1+; 938.1
(938.9370) (38.1) [{Zn(L-CH3O)}3 + H]1+; 1251.1 (1251.5799) (19.4) [{Zn(L-CH3O)}4 +
H]1+.
2.2.4 [Zn(HL-Cl)(OAc)(H2O)].2H2O 4: Anal. Calc. for C13H20ClN3O7Zn: C, 36.22; H, 4.66;
N, 9.75. Found: C, 36.77; H, 4.630; N, 9.905%. IR (KBr) (cm-1): 3388 coordinated water (O
– H), 3137 oxime (O – H), 1659 (OCO)asym. ), 1620 (C=N-N=C), 1520 (C=N)ox, 1426
(OCO)sym, 1035 (N–O). UV–Vis (EtOH, max/nm (log): 248 (4.01), 355 (4.10), 400 sh;
1H NMR (DMSO-d6, ppm): 1.91 (3H, CH3COO), 2.09 (3H, CH3–C=NN), 2.32 (3H, CH3–
C=NOH), 7.43, 7.44 ( 2H, aromatic), 8.06, 8.07 (2H, aromatic), 10.74 (2H, Coordinated
H2O), 13.42 (1H, oxime O–H). 13C{1H} NMR (DMSO-d6, ppm): 11.92 (CH3-C=N-OH),
14.23 (CH3-C=NN), 23.48 (CH3COO), 128.37, 128.58, 129.83, 130.04, 135.60 (CH-
aromatic), 148.86 (C=N-OH), 151.26 (C=NN), 172.82 (C6H5-CO), 177.20 (CH3COO). (+)
ESI – MS (DMF/CH3OH) m/z Calcd. (RA): 216.2 (216.5290) (2.0) [Zn(OAc)2(CH3OH) +
H+]1+; 248 (248.5710) (1.0) [Zn(OAc)2(CH3OH)2 + H+]1+; 257.3 (257.5813) (1.5)
[Zn(OAc)2(DMF) + H+]1+; 318.0 (318.0699) (12.0)
[Zn(HL-Cl)] 1+; 330 (330.6757 (2.0)
[Zn(OAc)2(DMF)2 + H+]1+; 350.2 (350.1119) (10.0) [Zn(OAc)(CH3OH)]1+; 378.2 (378.1223)
(10.0) [Zn(HL-Cl)(OAc) + H+]1+; 391.0 (391.1642) (6.0) [Zn(HL-Cl)(DMF)]1+, 451.0
(451.2166) (3.0) [Zn(HL-Cl)(OAc)(DMF) + H+]1+; 464.2 (464.2587) (3.7) [Zn(HL-
Cl)(DMF)2]1+; 524.0 (524.3109) (2.0) [Zn(HL-Cl)(DMF)2 + H+]1+; 653.2 (653.1469) (75.5)
[{Zn(L-Cl}2(H2O) + H+]1+; 695.2 (695.1842) (8.0) [{Zn(HL-Cl)}2(OAc)]1+; 708.0 (708.2261)

8
(8.5) [{Zn(L-Cl)}2 (DMF) + H+]1+; 781.2 (781.3206) (12.5) [{Zn(L-Cl)}2(DMF)2 + H+];952.0
(952.1936) (100) [{ZnL-Cl}3 + H+]1+; 1025.0 (1025.2880) (5.0) [{Zn(L-Cl)}3(DMF) + H+]1+;
1269.0 (1269.2556) (7.5) [{Zn(L-Cl)}4 + H+]1+.
2.2.5 [Zn(HL-NO2)(OAc)]3 5: Anal. Calc. for C13H14N4O6Zn: C, 40.28; H, 3.64; N, 14.45.
Found: C, 40.65; H, 3.69; N, 14.40%. IR(KBr) (cm-1): 3170 (O–H), 1620 (C=N-N=C),
1560 (OCO)asym., 1527 (C=N)ox, 1440 (OCO)sym, 1023 (N–O). UV–Vis (EtOH, max/nm
1
(log): 263 (4.40). 385 (4.39), 410 sh; H NMR (DMSO-d6, ppm): 1.92 (3H, CH3COO),
2.13, 2.15 (3H, CH3–C=NOH), 2.39, 2.41(3H, CH3-C=NN), 8.28, 8.29 (2H, aromatic), 8.33,
13
8.35 (2H, aromatic), 13.60 (H, oxime O–H). C{1H} NMR (DMSO-d6, ppm): 10.55, 11.37
(CH3-C=N-OH), 13.66, 13.94 (CH3-C=NN), 22.59 (CH3COO), 123.06, 123.19, 128.54,
128.68, 128.78 (CH-aromatic), 148.58 (C=N-OH), 152. 27 (C=NN), 170.59 (C6H5-CO),
177.50 (CH3COO). (+) ESI MS (DMF/CH3OH) m/z Calcd. (RA): 216.2 (216.5290) (2.5)
[Zn(OAc)2 (CH3OH) + H+]1+; 248.1 (248.5710) (2.5) [Zn(OAc)2(CH3OH)2 + H+]1+; 257.2
(257.5813) (3.5) [Zn(OAc)2(DMF) + H+]1+; 328.0 (328.6223) (7.5) [Zn(HL-NO2)]1+; 330.0
(330.6757) (3.8) [Zn(OAc)2(DMF)2 + H+]1+; 360.2 (360.6644) (8.2 ) [Zn(HL-
NO2)(CH3OH)]1+; 388.0 (388.6747) (8.5) [Zn(HL-NO2)(OAc) + H+]1+; 401.2 (401.7168)
(5.2) [Zn(HL-NO2)(DMF)]1+; 461.0 (461.7692) (2.0) [Zn(HL-NO2)(DMF) + H+]1+; 474.2
(474.8111) (2.0) [Zn(HL-NO2)(DMF)2 + H+]1+; 534.0 (534.8635) (3.5) [Zn(HL-NO2)(OAc)2
H+]1+; 674.0 (674.2520) (60.8) [{Zn(L-NO2)}2(H2O)+H+]1+ ; 729.0 (729. 3311) (9.5) [{Zn(L-
NO2)}2(DMF) + H+]1+; 802.0 (802.4256) (15.0) [{Zn(L-NO2)}2(DMF)2 + H+]1+; 983.2
(983.8511) (100) [{Zn(L-NO2)}3 + H+]1+; 1056.0 (1056.9456) (4.5) [{Zn(L-NO2)}3(DMF) +
H+]1+; 1311.0 (1311.4655) (6.0) [{Zn(L-NO2)}4 + H+]1+.
2.3 Physical measurement
Elemental analyses (C, H, N) were performed at the Micro analytical Laboratory, at Institut
fur Organische Chemie Technische Universitat, Darmstadt, Germany. The infrared spectra

9
were recorded on a Perkin-Elmer 1430 Data system and/or a Perkin-Elmer (FT-IR) Paragon
1000 PC spectrophotometer. Solid samples were examined as KBr discs. The UV-Vis
absorption spectra were recorded on V-530 Jasco, recording spectrophotometer, using 10 mm
quartz cells. 1H NMR and 13C NMR spectra were recorded on Bruker WM 300 and/or JEOL
500 MHz spectrometer using tetramethylsilane (TMS) as an internal standard. ESI mass
spectra were recorded on Esquire- LC from Bruker Daltonic Nebulizer 10psi (dry gas, 8Lmin-
1, dry temperature 250 ºC). X-ray diffraction data for [Zn(HL-H)(OAc)]2.H2O 1 and [Zn(HL-
CH3)(OAc)]2.H2O 2 complexes were collected on a Nonius CADY diffractometer, while
diffraction data for
[Zn(HL-Cl)(OAc)(H2O)].2H2O 4 and [Zn(HL-NO2)(OAc)]n 5,
complexes were collected on Oxford Diffraction Xcalibur (TM) single crystal X-ray
diffractometer with Sapphire CCD detector. Graphite monochromated Mo Kα radiation (λ =
0.71013Ǻ) was used in all cases. The structures were solved by direct methods with
SHELXS-97 [42] and refined with full-matrix least squares on F2 using SHELXL-97 [42].
Hydrogens were positioned with idealized geometry using a riding model and were refined
with isotropic displacement parameter. Drawings of the molecules were produced with
ORTEP3 [43] or PLATON [44]. Parameters of hydrogen bonds, and other non-covalent bond
interactions were measured using PLATON [44] and MERCURY (CCDC) [45]. Crystal data
and details concerning data collection and structure refinements for [Zn(HL-H)(OAc)]2.H2O
1, [Zn(HL-CH3)(OAc)]2.H2O 2, [Zn(HL-Cl)(OAc)(H2O)].2H2O 4, and [Zn(HL-NO2)(OAc)]n
5, are given in Table 1.
3. Results and Discussion
3.1 Synthesis and stoichiometry
The reaction of Zn(OAc)2.2H2O with aroylhydrazoneoximes having electron donating
substituents (H2L-R, R = H, p-CH3 and p-OCH3) in acidified ethanol using (1 : 1 molar ratio)

10
afforded the dinuclear Zn(II) complexes [{Zn(HL-R)(OAc)}2].H2O 1 – 3. However, on
using aroylhydrazoneoximes with electron withdrawing substituents (H2L-R, R = Cl and
NO2), the reaction proceeded with the formation of mononuclear [Zn(HL-
Cl)(OAc)(H2O)].2H2O (4) and trinuclear [{Zn(HL-NO2)(OAc)}3] (5).
3.2 Infrared Spectra
The IR spectra of Zn(II) acetate complexes 1 – 5, lack absorptions due to (N–H) ,
amide I [(C=O)] and amide II vibrations, but show intense absorption within the range
1610 – 1620 cm-1 due to (C=N–N=C ) of the deprotonated aroylhydrazone residue [46,47].
The spectra also show absorptions at 3130 – 3170, 1520 – 1535 and 1020 – 1030 cm-1,
respectively, due to hydrogen bonded oxime (O–H), (C=N)ox and (N–O) of the
hydroxyimino residue. These absorption bands are shifted to lower frequencies relative to
those of the free ligands. The recorded spectral patterns indicate the deprotonation of the
enolimine form of the aroylhydrazone residue while the oxime residue remains protonated
[37 – 40]. The aroylhydrazoneoxime ligand in these complexes acts as monoanionic NNO
tridentate ligand, coordinating to Zn(II) via azomethine hydrazone nitrogen, deprotonated
enolimine oxygen and oxime nitrogen [37 – 40].
The acetate anion in Zn(II) acetate complexes, generally, has versatile coordination
behavior, it can act as monodentate, chelating, bidentate bridging , monoatomic bridging and
chelating bridging ligands [48, 52]. The magnitude of the separation between the asymmetric
and symmetric carboxylate stretches, ∆ν = νas(OCO) – νs(OCO), is frequently used as a
diagnostic parameter for carboxylate binding mode in metal(II) complexes [53 – 58]. The IR
spectra of the dinuclear 1, 2 and 3 complexes display strong absorptions within the range
1628 – 1630 cm-1 due to acetate νas(OCO) vibration, while the corresponding νs(OCO)
vibrations appear within the range 1460 – 1470 cm-1. The average frequency separation ∆ν

11
between νas(OCO) and νs(OCO) is 163 cm-1 , suggesting syn – syn bidentate bridging (µ2 –
η1: η1) mode [50,53]. The spectra also show absorptions at 1580 – 1585 cm-1 and 1380 –
1387 cm-1 due to νas(OCO) and νs(OCO) respectively. The average value of ∆ν = 198 cm-1 is
in accordance with monoatomic bridging acetate (µ2 – η2: η0) coordination mode [55,58]. Both
monodentate and syn – syn bidentate bridging modes assigned for the acetate anions in 1 and
2 have been confirmed by X-ray structural analysis (section 3.5). The IR spectrum of the
mononuclear 4 complex displays the acetate νas(COO) and νs(COO) vibrations respectively at
1659 and 1426 cm-1 with frequency separation ( ∆ν = 233 cm-1) significantly higher than
that reported for ionic acetate (140 – 164 cm-1), indicating monodentate coordination mode
(µ1 – η1: η0) [55, 58]. This coordination mode has been also confirmed by X-ray molecular
structure (section 3.5). The νas(COO) and νs(COO) acetate vibrations in the spectrum of 5
complex appear respectively at 1560 and 1440 cm-1. The observed low value of ∆ν (120 cm-
1) relative to that of sodium acetate suggests syn – anti bidentate bridging coordination mode
(µ2 – η1: η1) [49,51,52,58] which is also confirmed by X-ray molecular structure (section 3.5).
Both of the stoichoimetry and IR spectral data of Zn(II) acetate complexes 1- 5 reveal
that the nuclearity and acetate coordination modes of these complexes are mainly influenced
by the nature of the substituent in the aroylhydrazone residue of the aroylhydrazoneoxime
ligand. Electron donating substituents in the dinuclear 1 – 3 complexes tend to increase the
formal negative charge (i.e increase in basicity) of the deprotonated enolimine oxygen of the
aroylhydrazone residue and hence decrease the formal positive charge (i.e decrease in Lewis
acidity) of the Zn(II) centers. This will favor the formation of the dinuclear structure where
the two Zn(II) centers are linked together by syn – syn bidentate and monoatomic bridging
acetate anions. On the other hand, electron withdrawing substituents (p-chloro and p-nitro) in
the aroylhydrazone residue resulted in a relative increase of the formal positive charge on
Zn(II). This leads to the formation of neutral mononuclear complex 4 where terminal

12
monodentate acetate anion is coordinated to the Zn(II) atom. To minimize the repulsion
between Zn(II) centers in polymeric complex 5, the successive Zn(II) centers are connected
together by syn – anti acetate bridges rather than syn – syn or monoatomic acetate bridges.
3.3 UV – Vis Absorption Spectra
The solution (UV – VIS) absorption spectra of the free aroylhydrazoneoxime ligands
H2L-R (R = H, p-CH3, p-OCH3, p-Cl, and p-NO3) (Scheme 1) in ethanol have been
previously reported [38 – 40]. The spectra display two intense absorptions, respectively, at
(230, 267 nm), (235, 278 nm), (244, 285 nm), (234, 280 nm) and (253, 295 nm) due to π∙∙∙π*
transitions. These absorption bands show red shift in the corresponding spectra of Zn(II)
acetate complexes 1 – 5 and appear at (240, 350 nm), (252, 357 nm), (265, 360 nm), (248,
355 nm) and (263, 285 nm) respectively. The spectra also show a new absorption, as a
shoulder, within the range (380 – 410 nm) due to MLCT transition [1, 6]. The observed
spectral changes, as compared to the spectra of free ligands, can be tentatively attributed to
the coordination of Zn(II) to H2L-R ligands which resulted in the deprotonation of the
enolimine tautomer and consequently form two π-delocalized 5,5-membered chelate rings.
This will extend conjugation along the ligand frame and resulted in a decrease of the energy
gap between n and π* orbitals. In the spectra of Zn(II) complexes 1 – 5, the absorptions due to
both π - π* and MLCT transitions depend on the nature of substituent in the terminal phenyl
group of the aroylhydrazone residue. The variation of the maximum absorption, expressed in
wave number (cm-1), as a function of Hammett substitution parameter (), Figure 1; suggests
two different excited states related to two different chromophores. The lower excited state
involves the aroylhydrazone chromophore (Scheme 2-a) where the negative charge is
localized on the deprotonated oxygen of the enolimine tautomer while the positive charge is
localized on the phenyl end. The higher excited state involves the diimine-oxime

13
chromophore (Scheme 2-b) where the positive charge is localized on the protonated oxygen
of the nitroso tautomer while the negative charge is localized on the phenyl end.
3.4 1H NMR and 13C NMR Spectra
The solution 1H NMR spectra of the dinuclear Zn(II) acetate complexes 1 – 3 in
DMSO-d6 display a pair of singlets at 2.08 – 2.14 ppm corresponding to the two methyl
groups adjacent to the oxime residue (CH3C=NOH), while the two methyl groups adjacent to
the aroylhydrazone residue (CH3C=NN) are more deshielded and appear as two singlets at
2.34 – 2.40 ppm. This behavior is in agreement with asymmetric dinuclear structure where
the two coordinated aroylhydrazoneoxime ligands are situated in different environments.
Similarly, the spectrum of the trinuclear [{Zn(HL-NO2)(OAc)}3] 5 also displays two singlets
for each of (CH3C=NOH) (2.13, 2.15 ppm) and (CH3C=NN) (2.39, 2.41 ppm) methyl
protons suggesting that in this trinuclear molecular unit, each of these methyl groups is
situated in two different orientations. The spectrum of the mononuclear [Zn(HL-
Cl)(OAc)(H2O)].2H2O 4 shows singlets at 2.09 and 2.321 ppm, respectively due to
(CH3C=NOH) and (CH3C=NN) methyl protons indicating mononuclear structure.
Furthermore, the spectra of Zn(II) acetate complexes 1 – 5 lack any signal that can be
attributed to hydrazinic NH proton indicating the deprotonation of the enolimine form of the
aroylhydrazone residue. The spectra, however, display broad signals within the range 11.33
– 11.75 and 13.36 – 13.56 ppm respectively due to intermolecular and intramolecular
hydrogen bonded oxime =NOH proton.
The solution 13C NMR spectra of 1 – 3, in DMSO-d6, also show pairs of resonances
at 10.50 – 11.6 and 13.5 – 14.45 ppm, respectively due to (CH3C=NOH) and (CH3C=NN)
methyl carbon nuclei. At lower field, the spectra also display pairs of resonances within the
range 142.40 – 150.90, 147.30 – 152.27 and 169.09 – 172.77 ppm, respectively due C=NOH,
C=NN and Ar.CO carbon nuclei. The spectrum of 4 however, show peaks at 11.92, 14.23,

14
148.86, 151.26 and 172.82 ppm, respectively attributed to CH3=NOH, CH3C=NN, C=NOH,
C=NN and Ar.CO carbon nuclei of the coordinated ligand. Here again the presence of only
one singlet for each of the carbon nuclei of the coordinated hydrazoneoxime ligands in the
13C NMR spectra of 4 is in agreement with mononuclear structure.
The 1H NMR spectra of the dinuclear Zn(II) acetate complexes 1 – 3 display one
singlet at 1.90 – 1.93 ppm for the acetate CH3 protons. The 13C NMR spectra also show two
resonances at 22.53 – 23.15 and 175.76 – 177.19 ppm respectively due to acetate CH3 and
OC(O) carbon nuclei. Both 1H NMR and 13C NMR spectra indicate that at ambient
temperature the bidentate bridging and monodentate bridging acetates in 1 – 3 complexes are
indistinguishable. This can be ascribed to a rapid reversible interconversion of the
monoatomic bridging acetate to syn-syn bidentate bridging acetate (carboxylate shift) at a
rate faster than NMR time scale [59]. This facile interconversion is due to the labile nature of
the spherical d10 configuration of Zn(II) [60] as well as the extremely fluxional acetate
coordination in these dinuclear complexes. The monoatomic bridging acetate plays a crucial
role in this carboxylate shift process [59]. The dangling oxygen of this monoatomic bridging
acetate initially interacts with Zn1 leading to a labile intermediate or transition state C,
Scheme 3, where O1 and O2 of monoatomic bridging acetate as well as O3 and O4 of
bidentate bridging acetate are linked respectively to Zn1 and Zn2 through semicoordinate
bonds. Simultaneous coordination of O1 to Zn1 and O3 to Zn2 followed by rotation around
O3 – C bond resulted in the transformation of monoatomic to bidentate bridging acetate as
shown in Scheme 3. Furthermore, the 1H NMR spectrum of 4 displays one singlet at 1.91 due
to acetate CH3 protons. The 13C NMR spectrum also show one singlet at 23.5 for CH3 carbon
in addition to another singlet at 177.20 ppm due to OC(O) carbon. The recorded spectra
suggest a mononuclear structure where the Zn(II) is, most probably coordinated to terminal
monodentate acetate.

15
3.5 ESI- Mass Spectra.
The (+) ESI-mass spectra of Zn(II) complexes 1 – 3 display peaks, of very low (RA)
values, corresponding to dinuclear [{Zn(HL-R)(OAc)}2 + H+]1+ and mononuclear [Zn(HL-
R)(OAc) + H+]1+ (R = H, CH3, and CH3O) species, while 4 and 5 complexes show only weak
peaks due to the mononuclear species [Zn(HL-R)(OAc) + H+]1+
(R = Cl and NO2),
suggesting extensive dissociation. The spectra of 1 – 5 complexes also show peaks
corresponding to [Zn(HL-R)(DMF)n + H+]1+ and [Zn(OAc)(DMF)n + H+]1+ (n = 0, 1 or 2)
generated, respectively, from the expulsion of OAc- and HL-R- anions, from [Zn(HL-
R)(OAc)(DMF)n + H+]1+. Deprotonation of the oxime group of the coordinated ligand,
during electrospray ionization leads to the formation of the mononuclear oximate [Zn(L-
R)(DMF)n]1+ cation followed by stepwise association reactions, through oximate bridge,
giving rise to di-, tri- and tetranuclear cations as shown in Scheme 4. This behavior has been
previously reported for Ni(II) and Cu(II) complexes derived from diacetylmonoxime
acyl/aroylhydrazone complexes [37 – 40].
3.5 Molecular Structures and Supramolecular Architectures
The x-ray crystal structures of 1, 2, 4 and 5 complexes reveal that the central Zn(II) in
these complexes is situated in a distorted square pyramidal environment. This is evident from
the calculated values of the tetragonality parameters, τ = [(β – α) / 60] [61], given in Table 2.
Bond distances and bond angles of the Zn(II) polyhedrons for 1, 2, 4 and 5 are listed,
respectively, in Tables ( S1 – S4). The x-ray structure of [{Zn(HL-H)(OAc)}2].H2O (1),
Figure 2, consists of dinuclear Zn(II) molecular unit and one solvate water molecule. Each
of Zn1 and Zn2 is coordinated to the mononegative NNO tridentate hydrazone oxime anion
(HL-H)– via oxime nitrogen (Zn1 – N3 = 2.177(10), Zn2 – N6 = 2.236(10) Å), imine
nitrogen (Zn1 – N1 = 2.003(10), Zn2 – N4 = 1.991(10) Å) and deprotonated enolimine

16
oxygen (Zn1 – O2 = 2.110(7), Zn2 – O6 = 2.058(8) Å), forming 5,5- bicyclic chelate ring.
The Zn1(HL-H) and Zn2(HL-H) moieties are linked together through the monoatomic
bridging acetate O1 oxygen (Zn1 – O1 = 1.974(8), Zn2 – O1 = 1.951(8) Å) and O4 and O5
oxygen atoms of the syn – syn bidentate bridging acetate (Zn1 – O4 = 1.935(10), Zn2 – O5 =
2.003(9) Å). The basal planes of Zn1 and Zn2 are defined, respectively, by oxime (N3 and
N6) nitrogen, imine (N1 and N4) nitrogen and deprotonated enolimine (O2 and O6) oxygen
of the mononegative tridentate hydrazoneoxime ligand. The fourth coordination site of both
Zn1 and Zn2 are occupied by the monoatomic bridging acetate O1 oxygen. The fifth apical
coordination sites for Zn1 and Zn2 are occupied, respectively, by O4 and O5 of the bidentate
bridging acetate oxygen’s. The Zn1 is separated from Zn2 by 3.257 Å and both Zn1 and Zn2
are, respectively, displaced from the corresponding basal plane by 0.500 and 0.416 Å towards
the apical bidentate acetate O4 and O5 oxygen.
The solvate water molecules in the crystal lattice of 1 play a crucial role in the process
of self assembly. Each two solvate water molecules act as bridges joining two binuclear
Zn(II) molecular units through reciprocal pairs of (O9H91∙∙∙O8, H91∙∙∙O8 = 1.987(9) Å)
hydrogen bonds (HB’s) between water H91 proton and uncoordinated monoatomic bridging
O8 oxygen, (O9H92∙∙∙O6, H92∙∙∙O6 = 2.021(9) Å) HB’s between water H92 and the
deprotonated enolimine O6 oxygen and (O9∙∙∙H3O, O9∙∙∙H3 = 1.873 Å) HB’s between water
O9 oxygen and oxime H3O proton, giving rise to supramolecular tetranuclear assembly.
These units are further linked together by reciprocal pairs of (C24H24C∙∙∙π1, H24C∙∙∙Cg1 =
2.887 Å), Table S5, between methyl C24H24C proton of the bidentate acetate and the
delocalized π system of the metalloaromatic chelate ring (N1, N2, C1.O2, Zn1) [62], giving
1
rise to D chain of supramolecular tetranuclear units propagating along a-axis (Figure 3-a).
The chains are further joined together via CH∙∙∙π interactions between methyl C23H23A

17
proton and aromatic ring (C12 – C17) π-system (C23H23a∙∙∙π2, C23H23a∙∙∙Cg2 = 3.009 Å)
generating 2D layer extended parallel to crystallographic ac- plane (Figure 3-b). The layers
are further interconnected by pairs of CH∙∙∙O, (C14H14∙∙∙O8, C14H14∙∙∙O8 = 2.641 Å) HB’s
3
forming D framework which is stabilized by (C23H23c∙∙∙π3, H23c∙∙∙Cg3 = 2.720 Å) and
(C7H7∙∙∙π3, C7H7∙∙∙Cg3 = 3.662 Å) CH∙∙∙π interactions (Table S5).
Similar to 1, the x-ray structure of [{Zn(HL-CH3)(OAc)}2].H2O (2), Figure 4,
consists of dinuclear molecular units where each of Zn1 and Zn2 is, respectively,
coordinated to the mononegative NNO tridentate hydrazoneoxime anion (HL-CH3)-1 via
oxime nitrogen (Zn1 – N1 = 2.186(2), Zn2 – N4 = 2.2284(19) Å) , imine nitrogen (Zn1 – N2
= 2.021(2), Zn2 – N5 = 2.0177(19) Å) and deprotonated enolimine oxygen (Zn1 – O1 =
2.1057(16), Zn2 – O6 = 2.8828 (17). The Zn1 and Zn2 are also coordinated to O4 and O5
oxygen atoms of the bidentate bridging acetate, in addition to O3 of the monodentate
bridging acetate (Zn1∙∙∙O3 = Zn2∙∙∙O3 = 1.9980 (16). Both Zn1 and Zn2 are displaced from
the corresponding basal planes (N1, N2, O1, O3) and (N4, N5, O6, O3) towards the bidentate
bridging acetate oxygen atoms O4 and O5 by 0.381 Å and 0.479 Å, respectively. The
distance between Zn1 and Zn2 (Zn1∙∙∙Zn2 = 3.376 Å) is relatively longer than that recorded
for complex 1. This can be attributed to the electron releasing effect of the p-CH3- substituent
of this dinuclear complex. The dinuclear molecular units are linked together via CH∙∙∙O
hydrogen bonds (C10H10c∙∙∙O4, C10H10∙∙∙O4 = 2.511 Å) and
(C12H12b∙∙π1,
C12H12b∙∙∙Cg1 =2.899 Å) CH∙∙∙π interactions, Table S6, giving rise to a helical chain
running along c-axis (c-chain) (Figure 5-a). The c-chains are associated together through
solvent water bridges via (O9H91∙∙∙N6, O91∙∙∙N6 = 2.136(4) Å) hydrogen bond (HB)
between water H91 proton and hydrazidic N6 nitrogen, (O9H92∙∙∙O6, H92∙∙∙O6 = 2.322(5) Å)
HB between water H92 proton and deprotonated enolimine O6, in addition to (O2H2∙∙∙O9,

18
O2H2∙∙∙O9 = 1.849(4) Å) between oxime H2 proton and water O9 forming 2D layer extended
parallel to bc-plane (bc layer). The layer structure is further stabilized by (C28H28A∙∙∙O6,
H28A∙∙∙O8 =2.665 Å) HB between methyl C28H28 proton and enolimine O6 oxygen as
shown in Figure 5-b. Two ac-layers are interconnected through (C14H14c∙∙∙O8,
C14cH14∙∙∙O8 = 2,878 Å) and (C24H24∙∙∙O8, C24H24∙∙∙O8 = 2.624 Å) HB’s generating 2D
double layered structure.
Different from the structures of 1 and 2, where the Zn(II) acetate complexes exist as
dinuclear molecular units, the x-ray structure of 4, Figure 6, consists of mononuclear
molecular unit [Zn(HL-Cl)(OAc)(H2O)] and two solvate water molecules. The basal plane of
4 is defined by oxime N3 nitrogen (Zn1 – N3 = 2.144 Å), imine N2 nitrogen (Zn1 – N2 =
2.057 Å), enoleimine O1 oxygen (Zn – O1 = 2.080 Å), and monodentate acetate O2 oxygen
(Zn1 – O2 = 1.962 Å). The coordinated water O5 oxygen is situated in the fifth apical
coordination site (Zn1 – O5 = 2.001 Å). The Zn1 is displaced from the basal plane (N3, N2,
O1, O2) towards acetate O5 oxygen by 0.431 Å. The coordinated water H51 proton and the
monodentate acetate O3 oxygen are involved in the formation of reciprocal pairs of CH∙∙∙O
hydrogen bonds (O5H51∙∙∙O3, H51∙∙∙O3 = 1.867 Å) giving rise to head to tail supramolecular
dimeric unit. These dimeric units are associated together through two solvent water bridges
via reciprocal pairs of (O7H71∙∙∙O2, H71∙∙∙O2 = 2.100 Å) Hydrogen bonds, between water
H71 proton and monodentate acetate O2 oxygen and (O7H72∙∙∙N1, H72 ∙∙∙N1 = 2.192 Å ) HB
between water H72 proton and hydrazidic N2 nitrogen, leading to the formation of 1D chain
running along c-axis (c-chain) (Figure 7). The c-chains are linked together through
(O6H61∙∙∙O1, H61∙∙∙O1 = 2-099 Å), (O6H62∙∙∙O7, H62∙∙∙O7 = 2.012 Å), (O5H52∙∙∙O6,
H52∙∙∙O6 = 1.896 Å) and (C6H6∙∙∙O5, H6∙∙∙O5 = 2.632 Å) CH∙∙∙O hydrogen bonds,
generating to 2D layer of dimeric units extended parallel to ac plane. The layers are further

19
interconnected through (C4H4∙∙∙O7, C4∙∙∙O7 = 3.465 Å), (C12H12A∙∙∙O6, C12∙∙∙O6 = 3.623
3
Å) and (C13H13C∙∙∙O4, C13∙∙∙O4 = 3.448 Å) CH∙∙∙O hydrogen bonds, forming D
framework, through which rectangular channels are running parallel to b-axis.
The x-ray crystal structure of [{Zn(HL-NO2)(OAc)}3] 5, Figure 8, consists of
trinuclear [{Zn(HL-NO2)(OAc)}3] molecular units which are linked together through syn -
anti bidentate bridged acetate anions, forming helical polymeric chain running parallel to b-
axis. The bond distances and bond angles of Zn1 polyhedron are listed in Table S4. The
oxime N1 nitrogen, imine N2 nitrogen and enolimine O1 oxygen of the coordinated
hydrazone oxime ligand in addition to the bidentate bridged acetate O2 oxygen constitute the
basal plane, while the bridged acetate O3 oxygen of the adjacent molecular unit occupies the
fifth apical site. The Zn1 is displaced from the basal plane (N1, N2, O1, O2), towards the
apical O3 oxygen, by 0.54 Å. The polymeric helical chain is stabilized by pairs of hydrogen
bonds between O4H4 oxime proton and O2 (O4H4∙∙∙O2, O4∙∙∙O2 = 3.071 Å) and O3
(O4H4∙∙∙O3, O4∙∙∙O3 = 2.751 Å) oxygen atoms of the syn – anti bidentate bridging acetate.
The helical chains are linked together via pairs of reciprocal hydrogen bonds between the O6
oxygen of the nitro group and C12H12A methyl proton (C12H12A∙∙∙O6, C12∙∙∙O6 = 3.443 Å)
and C3H3 aromatic proton (C3H3∙∙∙O6, C3∙∙∙O6 =3.287 Å), Table S8, giving a layer of
helical chains extended parallel to bc- plane. The layers are further connected to each other
through (C11H11C∙∙∙O5, C11∙∙∙O5 = 3.411 Å) hydrogen bond between the acetate methyl
C11H11C proton and nitro group O5 oxygen, in addition to CH∙∙∙π interaction between
methyl C13H13A proton and C2 – C7 aromatic ring π – system (C13H13A∙∙∙Cg1 = 3.085 Å),
Table S8, forming 3D framework structure.

20
3.6 Conclusion
The reaction of Zn(OAc)2.2H2O with substituted diacetylmonoxime aroylhydrazones
(H2L-R) (R = H, p-CH3, p-OCH3, p-Cl and p-NO2), using (1 : 1) molar ratio, in acidified
ethanol as a solvent afforded [{Zn(HL-H)(OAc)}2].H2O 1, [{Zn(HL-CH3)(OAc)}2].H2O 2,
[{Zn(HL-OCH3)(OAc)}2].H2O 3,
[Zn(HL-Cl)(OAc)(H2O)].2H2O 4,
[{Zn(HL-
NO2)(OAc)}3]n 5 respectively. Both nuclearity and acetate coordination modes in 1 – 5
complexes are affected by the nature of the substituent in the terminal phenyl group of the
hydrazide moiety. Electron donating substituent (R = H, CH3, OCH3) in 1 – 3 complexes tend
to decrease the formal positive charge of Zn(II) and favor the formation of dinuclear
complexes. In 1 – 3 complexes, the Zn(II) atoms are linked together by syn – syn and
monoatomic bridging acetate anions. Electron withdrawing substituents (R = Cl and NO2) in
4 and 5 complexes resulted in an increase of the formal positive charge of Zn(II). To avoid
repletion between Zn(II) atoms mononuclear Zn(II) acetate complex 4 as well as linear chain
polymer 5 were obtained. In 4 the terminal acetate acts as monodentate anion, while in 5 the
Zn(II) atoms are linked together by syn – anti bridging acetate anions.
The electronic absorption spectra of Zn(II) acetate complexes 1 – 5 reveal that both
electron donating or electron withdrawing substituents in the hydrazide residue resulted in a
red shift for both π – π* and MLCT absorption bands. This behavior suggests two different
excited states originated from the excitation of keto/enol aroylhydrazone moiety and
oxime/protonated nitroso chromophores.

21
Supplementary data
CCDC 1985722, 1985613, 1985620, 1985619 contain the supplementary crystallographic
data for 1, 2, 4 and 5 complexes, respectively. These data can be obtained free of charge via
http://www.ccdc.Cam.ac.uk/conts/retrieving.html, or from Cambridge crystallographic Data
center, 12 Union Road Cambridge CB2 IEZ, UK (fax: +44-1223-336033; e-Mail:
deposit@ccdc.ac.uk or www: http://www.ccdc.cam.ac.uk.
Supplementary material
Contains Tables for bond distances, bond angles and structural parameters of non covalent bond
interactions for 1, 2, 4, 5 complexes
ACKNOWLEDGEMENT
Dr. Nahed M. H. Sallem would like to thank Faculty of Science, Alexandria University for supporting
the present work through “Science Research Enhancement Program (Science REP) 2011.
Author statement
Nahed Salem, carried out all the experimental work, collect the experimental results and writing the
experimental section; Sabina foro , solved the x-ray crystal structures and collecting the x-ray
structural data; M. Iskander , discuss and interpret the data, writing and editing the text including
all art work.
Conflict of interest
The authors declare that they have no known competing financial interests or personal relationship
that could have appeared to influence the work reported in this paper.
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25
List of changes and rebuttals
1) The title of the paper has been diminished.
2) Parentheses between the numbers of complexes have been deleted.
3) Polynuclear or multinuclear complexes, in this article, are coordination compounds
containing two or more metal atoms or ions in single coordination sphere. The metallic
centers are bounded together through metal – metal bonds , bridging ligands or ligands
substituted with subistituents having donor atoms which can coordinate with one or more
metallic centers.
Polymeric metal complex or coordination polymer is a coordination
complex between polymeric matrix consists of a chain of monomeric bi-, tri or
mutidentate ligand capable to bound one or more metallic ion forming polymeric linear or
helical chain. Polymeric Chains of di-, tri…or metallic cluster can be also considered as
coordination polymers.
4) Information concerning multinuclear Zn(II) acetate acyl/aroylhydrazones as well as
diacetylmonoxime acyl/aroylhydrazones complexes have been introduced in the
Introduction section.
5) Only four parts (I, II. III and V) (ref. 37 – 40) of this series of ( coordination chemistry of
hydrazoneoxime ligands) are concerned with the coordination chemistry Cu(II) and Ni(II)
complexes with diacetylmonoxime acyl/aroylhydrazones. Part IV deals with complexes
derived from diacetylmonoxime S-benzylhydrazinedithiocarboxylate. The new aspects of
the present article (part VI) are given at the end of introduction section.
6) In the experimental section, H2L-R (1,R….)1, is meaningless and has been omitted .
7) 1HNMR and 13HNMR have been corrected.
8) The rapid interconversion from monodentate to bidentate acetate ligands in solution, given
in the text, is based on NMR studies at room temperature. However, the reaction
mechanism given in Scheme 3 is a well established mechanism based on dynamic NMR
studies at different temperature (ref. 59) and not speculative. This part is very important to
understand and appreciate the carboxylate shift process usually observed in Zn(II) acetate
complexes. Also, it is of interest , at least from the educational point of view.

26
9) The correct word is singlets not signals.

27
[Zn(HL-H )(OAc)]2.H2O (1) [Zn(HL-CH3)(OAc)]2.H2O
(2)
[Zn(HL-
Cl)(OAc)(H2O)].2H2O (4)
[Zn(HL-NO2)(OAc)]n (5)
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
C26H32N6O9Zn2
703.32
293(2)
C28H36N6O9Zn2
731.37
299(2)
C13H20ClN3O7Zn
431.14
293(2)
0.71073
Triclinic
P-1
C13 H14N4 O6Zn
387.65
293(2)
0.71073
1.54180
0.71073
Monoclinic
P21/c
Monoclinic
P21/c
Monoclinic
P21/c
Unit cell dimensions
15.890(2)
10.639(2)
17.963(3)
90
93.12(2)
90
12.962(2)
18.580(3)
13.780(2)
90
98.02(2)
90
7.704(1)
9.159(1)
13.198(2)
95.46(1)
100.70(2)
95.52(2)
8.206(1)
6.6160(8)
14.865(2)
90
103.03(1)
90
a (Å)
b (Å)
c (Å)
α (º)
β (º)
γ (º)
Volume (Å3)
Z
3032.2(9)
4
3286.2(9)
4
904.7(2)
2
786.25(17)
2
Calculated density
(Mg/m3)
1.541
1.478
1.583
1.637
Absorption coefficient
(mm-1)
1.642
2.300
1.544
1.600
F(000)
1448
1512
444
396
Crystal size (mm)
Θ range for data
collection(˚)
Limiting indices
0.10x0.08x0.01
2.54 to 26.37
0.55x0.55x0.50
3.44 to 66.99
0.24x0.14x0.08
2.60 to 26.37
0.40 x 0.12 x 0.02
2.55 to 26.37
-19<=h<=17, -12<=k<=13,
-11<=1<=22
-15<=h<=13, -22<=k<=26,
-16<=1<=16
-9<=h<=7, -10<=k<=11, -
15<=1<=16
-10<=h<=7, -8<=k<=6, -
18<=l<=18
Reflections collected
/unique
12101/6064[R(int) =
0.2502]
11089/5854[R(int) =
0.0562]
6473/3692[R(int) = 0.0206]
3046 / 2334 [R(int) =
0.0206]
Completeness to θ
Max. and min.
transmission
26.37 97.9%
0.9838 and 0.8530
66.99 99.9%
0.3168 and 0.2940
26.37 99.5%
0.8864 and 0.7082
26.37 99.7%
0.9687 and 0.5669
Absorption correction
Semi-empirical from
equivalents
Psi-scan
Semi-empirical from
equivalents
Semi-empirical from
equivalents
Refinement method
Full-matrix least –squares
on F2
Full-matrix least –squares
on F2
5854/0/427
Full-matrix least –squares on
F2
3692/7/250
Full-matrix least –
squares on F2
2334 / 1 / 222
1.060
R1 = 0.0329, wR2 =
0.0760
Data/restraints/parameters 6064/68/394
Goodness-of-fit on F2
0.660
Final
1.144
1.092
R
indices R1 = 0.0782, wR2 = 0.0531
R1 = 0.3980, wR2 = 0.0966
R1=0.0359, wR2=0.0920
R1=0.0453, wR2=0.0956
[I>2sigma(I)]
R indices (all data)
R1=0.0389, wR2=0.0934
R1=0.0672, wR2=0.1068
R1 = 0.0402, wR2 =
0.0799
Table 1:
Crystal data and structure refinement parameters for [{Zn(HL-H )(OAc)}2].H2O 1, [{Zn(HL- CH3)
(OAc)}2].H2O 2, [Zn(HL-Cl)(OAc)(H2O)].2H2O 4 and [Zn(HL-NO2)(OAc)]3 5.

28
Complex
α ( º )
β ( º )
τ
1, Zn1
N1 – Zn1 – O1 = 135.5
N4 – Zn2 – O1 = 147.2
N3 – Zn1 – O2 = 151.8
N6 – Zn2 – O6 = 149.8
0.272
0.043
Zn2
2, Zn1
N2 – Zn1 – O3 = 146.0
N5 – Zn2 – O3 = 139.2
N1 – Zn1 – O1 = 149.7
N4 – Zn2 – O6 = 150.0
0.062
0.180
Zn2
4, Zn1
5, Zn1
N2 – Zn1 – O2 = 139.8
N2 – Zn1 – O2 = 135.4
N3 – Zn1 – O1 = 149.4
N1 – Zn1 – O1 = 148.0
0.160
0.210
Table 2: Tetragonality parameters (τ) calculated for 1, 2, 4 and 5 Zn(II) acetate complexes

29
Scheme 1
Scheme 2: Excited states involved in the absorption spectra of Zinc(II) acetate complexes (1
– 5).