In
this contribution we have extended our current research goal
of designing functional metal–organic frameworks (MOFs) using
bispyrazole type ligands. Accordingly, ten new cobalt-based MOFs have
been synthesized using a simple bispyrazole ligand, 4,4′-methylene-bispyrazole
(H2MBP), and isophthalic acid (H2IPA) and its
four 5-substituted derivatives R-H2IPA (R = COOH, OH, tBu, NH2). The major aim of this study was to validate
the mutual influence of temperature and substitutions on the final
structural self-assembly. Five different isophthalic acid derivatives
were used to study the influence of substituents while each reaction
was carried out at two different temperatures to assess the temperature
effect. A clear correlation was observed between the reaction temperature
and the coordination number of the cobalt atoms which consequently
changes the self-assembly pattern. We have also shown that the periodical
change in coordination number did bring about some systematic changes
in the structural network via secondary building unit selectivity.
With the presence of a tunable cavity inside the network, high surface
area, and unsaturated metal centers, MOFs show highly encouraging
photocatalytic degradation of toxic dye molecule with a potential
application in wastewater purification. Another fascinating aspect
of this work is the construction of magnetic coordination polymers
with the occurrence of a not-so-common MCE behavior of cobalt-based
MOF.
A novel Fe(III) based gel was synthesized via self-assembly of Fe(III) and pyridine 2,6 dicarboxylic acid. The synthesized gel has remarkable mechanical strength as well as self sustainability. The metallogel...
In this contribution we have carried out a systematic magnetostructural investigation to establish a robust one-to-one correlation between quasi-orthogonal bridging mode of pyrazolate ring and ferromagnetism coupling. Generating a...
This contribution
deals with the synthesis and utilization of a
new pyrazole-based unsymmetrical ligand, 3-(3-carboxyphenyl)-1
H
-pyrazole-5-carboxylic acid (H
2
CPCA), for generating
multifunctional materials. The reaction with the Co(II) salt in the
presence of a co-ligand 2,9-dimethyl phenanthroline (dmphen) results
in the formation of the helical compound {[Co
2
(dmphen)
2
(CPCA)
2
]DMF}
n
(
1
). However, two isostructural monomeric complexes are formed
{[M(HCPCA)
2
(H
2
O)
2
], M = Co(II), (
2
) and Mn(II) (
3
)} when reactions were carried
out in the absence of dmphen. Compound
1
shows some highly
encouraging single-ion magnetic (SIM) properties. Detailed magnetic
studies unveil slow relaxation of magnetization of compound
1
, driven by the higher magnetic anisotropy of the cobalt
ion, with the energy barrier of ∼9.2 K and relaxation time
of 9.1 × 10
–5
s, suggesting a SIM behavior.
Moreover, UV–vis and fluorescence studies confirm the selective
dye degradation of compound
1
with methylene blue both
in the presence and absence of H
2
O
2
, with the
remarkable degradation efficiency of ∼98 and ∼82%, respectively.
Two newly synthesized Fe(III) based complexes, [Fe 4 L 2 (μ 3 -O) 2 (Cl) 2 (MeOH) 4 (H 2 O) 4 ](ClO 4 ) 2 •4H 2 O•MeOH (1) and [Fe 2 L 3 ]•4DMF (2) were isolated in solid crystalline form using the reaction of iron(III) perchlorate with the ligand H 2 L (H 2 L = 6,6′-((1E,1′E)-hydrazine-1,2-diylidenebis(methanylylidene))bis(2-methoxyphenol). (DMF= N,N-dimethylformamide, MeOH = methanol). Compound 1 was self-assembled in MeOH, but when the solvent was changed to DMF, compound 2 was harvested. Furthermore, compound 1 was converted to compound 2 just by dissolving compound 1 in DMF. Sequential self-assembly and conversion of compound 1 to 2 were monitored by UV−vis spectroscopy and ESI-Mass spectroscopy in solution phase. Single crystal X-ray analysis showed that compound 1 has μ 3 -oxo bridged tetranuclear structure whereas compound 2 has puckered dinuclear structure. Magnetic studies indeed revealed frustrated magnetic spin for compound 1 whereas antiferromagnetic interaction was observed for compound 2. The spectrophotometrical investigation on their phosphatase like activity revealed remarkable hydrolytic efficiency for both the complexes. Michaelis−Menten-derived kinetic parameters suggest the competitiveness of the rate of P−O bond fission employing the phosphomonoester (4-nitrophenyl)phosphate (PNPP) in 97.5% DMF is 1 > 2, and the k cat value lies in the range 28.95−38.43 s −1 at 298 K. Computational calculations have verified the higher catalytic activity of compounds 1 over 2 attributed to the large number of labile groups attached to the metal centers.
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