Preparation of Co3O4 Nanoparticles via Thermal Decomposition of Three New Supramolecular Structures of Co(II) and (III) Containing 4′-Hydroxy-2,2′:6′,2′′-Terpyridine: Crystal Structures and Thermal Analysis Studies

Abstract

Three cobalt(II) and (III) complexes based on the 4′-hydroxy-2,2′:6′,2"-terpyridine (tpyOH) have been synthesized and structurally characterized by X-ray crystallography. The reaction of tpyOH with CoCl2·6H2O in a mixture of methanol/CH2Cl2 resulted in the formation of the new complex [CoIICl2(tpyOH)] (1). On the other hand, the reaction of CoCl2·6H2O with tpyOH in a 2:1 or 1:1 mol ratio in methanol under reflux condition affords the new complexes [CoIII(tpyOH)(tpyO)][CoIICl4]·H2O (2) and [CoIIICl2(H2O)(tpyO)]·H2O (3), respectively. Moreover, the treatment of a methanolic solution of CoCl2·6H2O with tpyOH in a branched tube at 60 °C resulted in the formation of three quality crystals of the complexes 1 and 2 as the major products as well as the complex 3 as a minor product. The crystal structure of [CoCl2(tpyOH)] (1) reveals that the cobalt(II) is penta-coordinated by two Cl⁻ and three nitrogen atoms of tpyOH in a distorted square pyramidal geometry. The complex [CoIII(tpyOH)(tpyO)][CoIICl4]·H2O (2) is described as a highly distorted octahedral geometry [CoN6] while the X-ray crystal structure of the complex [CoIIICl2(H2O)(tpyO)]·H2O (3) shows that cobalt(III) is hexa-coordinated in a slightly distorted octahedral geometry CoCl2N3O. Several strong noncovalent interactions are present in the crystal structure of 1–3. The hydrogen bonding in 1 involves the OH⋯Cl bridges while there is a hydrogen bonding between tpyO and tpyOH of the next molecule in 2 and hydrogen bridges and π–π interactions for 3, connecting molecules and ions in the crystalline 1–3 to form supramolecular networks. The thermal stabilities of the cobalt complexes reveal that the loss of free terpyridine ligand could not be observed in low temperatures. The hexagonal and spherical Co3O4 nanoparticles (NPCs) were prepared by direct calcination of complexes 1–3 at 600 °C in air. The nanostructures of the products were characterized by IR, powder X-ray diffraction, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy which show the purity of the resulting Co3O4 NPCs. The average particle size using Scherrer’s equation is calculated to be about 32–35 nm.

Full text

Vol.:(0123456789)
1 3
J Inorg Organomet Polym (2018) 28:235–250
DOI 10.1007/s10904-017-0706-6
Preparation of Co3O4 Nanoparticles viaThermal Decomposition
ofThree New Supramolecular Structures ofCo(II) and(III)
Containing 4′-Hydroxy-2,2′:6′,2′′-Terpyridine: Crystal Structures
andThermal Analysis Studies
BadriZ.Momeni1· FarzanehRahimi1· FrankRominger2
Received: 20 August 2017 / Accepted: 13 October 2017 / Published online: 20 October 2017
© Springer Science+Business Media, LLC 2017
crystalline 1–3 to form supramolecular networks. The ther-
mal stabilities of the cobalt complexes reveal that the loss
of free terpyridine ligand could not be observed in low tem-
peratures. The hexagonal and spherical Co3O4 nanoparticles
(NPCs) were prepared by direct calcination of complexes
1–3at 600°C in air. The nanostructures of the products were
characterized by IR, powder X-ray diffraction, field emission
scanning electron microscopy and energy-dispersive X-ray
spectroscopy which show the purity of the resulting Co3O4
NPCs. The average particle size using Scherrer’s equation
is calculated to be about 32–35nm.
Keywords Cobalt· Terpyridine· Crystal structure·
Co3O4 NPCs· Thermal analysis
1 Introduction
Transition metal complexes of 2,2′:6′,2′′-terpyridine ligand
have been studied extensively since the ligand was first
reported at 1932 by Morgan and Burstall [1]. A vast num-
ber of methods are known for the preparation of substi-
tuted terpyridines. Most of these methods are based on
the 2-acetyl pyridines and aryl aldehydes [2–5]. 4-Sub-
stituted-2,6-diacetylpyridines have been used to prepare
2,2′:6′,2"-terpyridine functionalized at C4′ and containing
substituents at C4, C5 and C6 of both terminal pyridines [6].
Terpyridine complexes of transition metals such as cobalt
have attracted considerable interest due to their applica-
tions in medicinal chemistry, catalysis, crystal engineering
and supramolecular chemistry [7–12]. The use of ligands
with multiple-metal binding domains is of particular inter-
est, since they can be linked by a metal-containing moiety
instead of an organic group, such as 4′-pyridyl, carboxylic
acid, hydroxy or 4′-carboxyphenyl-2,2′:6′,2′′-terpyridines
Abstract Three cobalt(II) and (III) complexes based on the
4′-hydroxy-2,2′:6′,2"-terpyridine (tpyOH) have been synthe-
sized and structurally characterized by X-ray crystallogra-
phy. The reaction of tpyOH with CoCl2·6H2O in a mixture
of methanol/CH2Cl2 resulted in the formation of the new
complex [CoIICl2(tpyOH)] (1). On the other hand, the reac-
tion of CoCl2·6H2O with tpyOH in a 2:1 or 1:1mol ratio in
methanol under reflux condition affords the new complexes
[CoIII(tpyOH)(tpyO)][CoIICl4]·H2O (2) and [CoIIICl2(H2O)
(tpyO)]·H2O (3), respectively. Moreover, the treatment
of a methanolic solution of CoCl2·6H2O with tpyOH in a
branched tube at 60°C resulted in the formation of three
quality crystals of the complexes 1 and 2 as the major prod-
ucts as well as the complex 3 as a minor product. The crystal
structure of [CoCl2(tpyOH)] (1) reveals that the cobalt(II) is
penta-coordinated by two Cl− and three nitrogen atoms of
tpyOH in a distorted square pyramidal geometry. The com-
plex [CoIII(tpyOH)(tpyO)][CoIICl4]·H2O (2) is described as a
highly distorted octahedral geometry [CoN6] while the X-ray
crystal structure of the complex [CoIIICl2(H2O)(tpyO)]·H2O
(3) shows that cobalt(III) is hexa-coordinated in a slightly
distorted octahedral geometry CoCl2N3O. Several strong
noncovalent interactions are present in the crystal structure
of 1–3. The hydrogen bonding in 1 involves the OH⋯Cl
bridges while there is a hydrogen bonding between tpyO and
tpyOH of the next molecule in 2 and hydrogen bridges and
π–π interactions for 3, connecting molecules and ions in the
* Badri Z. Momeni
momeni@kntu.ac.ir
1 Faculty ofChemistry, K.N. Toosi University ofTechnology,
P.O. Box16315-1618, Tehran15418, Iran
2 Organisch-Chemisches Institut, Universität Heidelberg,
69120Heidelberg, Germany
Content courtesy of Springer Nature, terms of use apply. Rights reserved.