•CPs and MOFs built up with poly(pyrazole)- and poly(pyrazolate)-based ligands and transition metals.•Thermal behaviour, structural aspects and functional properties of poly(pyrazolyl)-based CPs and ...MOFs.•Copper, zinc, cobalt, nickel, cadmium, silver and iron CPs and MOFs possessing functional properties of economic, technological and/or environmental interest.
In the past two decades, the vast classes of coordination polymers (CPs) and metal–organic frameworks (MOFs) have received deep attention in both the academic and industrial realms, as they can possess different functional properties of economic, technological and/or environmental interest, such as luminescence, electric conductivity, magnetism, catalytic activity, gas storage or separation, drug delivery – to mention only a few.
Within this vast landscape, this review proposes a survey on those transition metal containing CPs and MOFs built up with poly(pyrazole)- and poly(pyrazolate)-based ligands, in which up to three N-donor heterocyclic rings are organized on rigid or flexible cores. The overview has been restricted to the most recurrent transition metals, namely copper, zinc, cobalt, nickel, cadmium, silver and iron. For each material, mentioning of the synthetic method(s) yielding to its isolation is complemented by a description of its thermal behaviour, of the main structural aspects and, whenever investigated, of its functional properties.
Two isoreticular series of pyrazolate-based 3D open metal–organic frameworks, MBDP_X, adopting the NiBDP and ZnBDP structure types H2BDP = 1,4-bis(1H-pyrazol-4-yl)benzene, were synthesized with the ...new tagged organic linkers H 2 BDP_X (X = −NO2, −NH2, −OH). All of the MBDP_X materials have been characterized through a combination of techniques. IR spectroscopy proved the effective presence of tags, while X-ray powder diffraction (XRPD) witnessed their isoreticular nature. Simultaneous TG/DSC analyses (STA) demonstrated their remarkable thermal stability, while variable-temperature XRPD experiments highlighted their high degree of flexibility related to guest-induced fit processes of the solvent molecules included in the channels. A structural isomer of the parent NiBDP was obtained with a sulfonate tagged ligand, H 2 BDP_SO 3 H. Structure solution from powder diffraction data collected at three different temperatures (room temperature, 90, and 250 °C) allowed the determination of its structure and the comprehension of its solvent-related flexible behavior. Finally, the potential application of the tagged MOFs in selective adsorption processes for gas separation and purification purposes was investigated by conventional single component adsorption isotherms, as well as by advanced experiments of pulse gas chromatography and breakthrough curve measurements. Noteworthy, the results show that functionalization does not improve the adsorption selectivity (partition coefficients) for the resolution of gas mixtures characterized by similar high quadrupole moments (e.g., CO2/C2H2); however, the resolution of gas mixtures containing molecules with highly differentiated polarities (i.e., N2/CO2 or CH4/CO2) is highly improved.
Tunable hydrophobicity: Efficient air filters for the protection against chemical warfare agents might be achieved by surface functionalization of the pores in robust metal–organic frameworks (MOFs) ...with fluoroalkyl residues and the precise control of their pore size (see picture). These MOFs capture harmful volatile organic compounds even under extremely moist conditions (80 % relative humidity).
Two highly porous coordination polymers, containing rare octanuclear hydroxo-nickel clusters and long bis-pyrazolyl spacers, are shown to possess, after mild thermal treatment, lattice cavities up to ...72% of the total crystal volume.
Atomic‐level control over the position and growth of a single and continuous metal chain is an ambitious goal that often requires complex and costly processes. Herein, we demonstrate that 1Pd‐DNA ...molecules, comprising a continuous single chain of PdII ions, can be prepared by a simple self‐assembly reaction between the complex Pd(Cheld)(CH3CN) (1Pd_CH3CN) (Cheld=chelidamic acid) and single‐stranded DNA homopolymers (ss‐DNA) containing adenine (A) or 7‐deazaadenine (X) bases. The single PdII‐base pairs 1Pd(N1‐A) and 1Pd(N1‐X) were synthesized and characterized in solution and solid‐state (X‐ray diffraction) revealing an arrangement similar to that of natural Watson–Crick base pairs. Subsequently, 1Pd‐DNA hybrids were prepared, characterized, and their structures studied by small‐angle X‐ray scattering (SAXS) and ab‐initio calculations. The results indicate that the 1Pd‐DNA structures resemble that of double‐stranded DNA, with one strand being replaced by a supramolecular stack of continuous PdII complexes.
Pd‐DNA hybrids with an uninterrupted one‐dimensional PdII array running through the center of the helixes have been prepared using a bottom‐up approach by a self‐assembly reaction between adenine homopolymers (dA) and complementary palladium complexes. The complexes bind to each adenine forming sequential Watson–Crick Pd‐mediated base pairs.
The metal–organic frameworks (MOFs) M(BPZNO2) (M=Co, Cu, Zn; H2BPZNO2=3‐nitro‐4,4′‐bipyrazole) were prepared through solvothermal routes and were fully investigated in the solid state. They showed ...good thermal stability both under a N2 atmosphere and in air, with decomposition temperatures peaking up to 663 K for Zn(BPZNO2). Their crystal structure is characterized by 3D networks with square (M=Co, Zn) or rhombic (M=Cu) channels decorated by polar NO2 groups. As revealed by N2 adsorption at 77 K, they are micro‐mesoporous materials with BET specific surface areas ranging from 400 to 900 m2 g−1. Remarkably, under the mild conditions of 298 K and 1.2 bar, Zn(BPZNO2) adsorbs 21.8 wt % CO2 (4.95 mmol g−1). It shows a Henry CO2/N2 selectivity of 15 and an ideal adsorbed solution theory (IAST) selectivity of 12 at p=1 bar. As a CO2 adsorbent, this compound is the best‐performing MOF to date among those bearing a nitro group as a unique chemical tag. High‐resolution powder X‐ray diffraction at 298 K and different CO2 loadings revealed, for the first time in a NO2‐functionalized MOF, the insurgence of primary host–guest interactions involving the C(3)–NO2 moiety of the framework and the oxygen atoms of carbon dioxide, as confirmed by Grand Canonical Monte Carlo simulations. This interaction mode is markedly different from that observed in NH2‐functionalized MOFs, for which the carbon atom of CO2 is involved.
Catching on: As CO2‐capture materials, NO2‐functionalized bis(pyrazolate) metal–organic frameworks (MOFs) adsorb 21.8 wt % CO2 under ambient conditions. A preferential O(CO2)–C‐NO2 interaction is confirmed by experiment and theory. These compounds are the best‐performing MOFs to date among those bearing a nitro group as a unique chemical tag.
The novel zinc(II) µ-oxo-bridged-dimeric complex Zn
(µ-O)
(BMIP)
(BMIP = 1,3-bis(5-methoxy-1-methyl-1
-indol-3-yl)propane-1,3-dione),
, was synthetized and fully characterized. The spectral data ...indicate a zincoxane molecular structure, with the BMIP ligand coordinating in its neutral form via its oxygen atoms. Structural changes in
in dimethylsulfoxide (DMSO) were evidenced by means of spectroscopic techniques including infrared absorption and nuclear magnetic resonance, showing DMSO entrance in the coordination sphere of the metal ion. The resulting complex Zn
(µ-O)
(BMIP)
(DMSO),
, readily reacts in the presence of
-methyl-imidazole (NMI), a liquid-phase nucleoside mimic, to form Zn
(µ-O)
(BMIP)
(NMI),
, through DMSO displacement. The three complexes show high thermal stability, demonstrating that
has high affinity for hard nucleophiles. Finally, with the aim of probing the suitability of this system as model scaffold for new potential anticancer metallodrugs, the interactions of
with calf thymus DNA were investigated in vitro in pseudo-physiological environment through UV-Vis absorption and fluorescence emission spectroscopy, as well as time-resolved fluorescence studies. The latter analyses revealed that Zn
(µ-O)
(BMIP)
(DMSO) binds to DNA with high affinity upon DMSO displacement, opening new perspectives for the development of optimized drug substances.
Hydrocarbons separation in petrochemical industries is a key, energy-consuming stage in the manufacture of high-quality added-value products—hence the need for more efficient materials and ...environmentally friendly methodologies to improve this process. In this context, we have studied the effect of metal-organic frameworks (MOFs) pore functionalization in hexane isomers separation, isolating the robust isoreticular zinc(II) bipyrazolates Zn(BPZ), showing no pore decoration, Zn(Me
2
BPZ), the pores of which are decorated with apolar methyl groups, and Zn(BPZ(NH
2
)
2
), the spacers of which possess polar Lewis-basic functions (H
2
BPZ = 1
H
,1′
H
-4,4′-bipyrazole; H
2
Me
2
BPZ = 3,3′-dimethyl-1
H
,1′
H
-4,4′-bipyrazole; H
2
BPZ(NH
2
)
2
= 3,5-diamino-1′
H
,1′
H
-4,4′-bipyrazole; DMF = dimethylformamide). After characterizing Zn(BPZ(NH
2
)
2
) as per its crystal structure and thermal behaviour, and all the three MOFs as per their textural properties, we investigated, from the experimental and computational points of view, the impact of the square one-dimensional channels decoration on the separation of the hexane isomers, demonstrating the relevance of pore constrictions in the resolution of the title alkanes mixture.
A new polycrystalline vapochromic polymorph of the one-dimensional copper bispyrazolate polymer reversibly and selectively absorbs a number of small molecules; the crystal structures of the anhydrous ...and fully hydrated species, determined by powder diffraction methods, are markedly different despite their simple, fast, and reversible interconversion.
Alkenylureas arising from glycine allylamides were proven to be suitable substrates for the synthesis of bicyclic five‐membered ring‐fused piperazinones. The reported intramolecular domino processes, ...performed under oxidative conditions with bis(acetonitrile)palladium dichloride as catalyst and copper(II) chloride in a stoichiometric amount by microwave activation, were completely selective, involving either diamination or aminooxygenation. While the latter process is determined by the direct intervention of the urea oxygen on the σ‐alkylpalladium intermediate, the diamination reaction can in principle derive from a direct attack of the second nitrogen atom on the palladium complex or on the first formed chloromethylpiperazinone. Indeed, this latter species was isolated and proved to be capable of conversion solely into the imidazopiperazinone.
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