- Solvent-Induced Reversible Spin-Crossover in a 3D Hofmann-Type Coordination Polymer and Unusual Enhancement of the Lattice Cooperativity at the Desolvated State
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The new 3D Hofmann-type coordination polymer [Fe(dpyu){Pt(CN)4}]·9H2O [dpyu = 1,3-di(pyridin-4-yl)urea] exhibits reversible interchange between two- and one-step spin-crossover behavior, associated with desorption/resorption of lattice water molecules. Solvent water removal also induces an increase of the spin-transition temperature, indicating strong lattice cooperativity, observed for the first time in a 3D Hofmann-type coordination polymer.
- Konar, Sanjit,Mondal, Dibya Jyoti,Roy, Subhadip,Yadav, Jyoti,Zeller, Matthias
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- Size-Selective Urea-Containing Metal-Organic Frameworks as Receptors for Anions
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Anion recognition by neutral hosts that function in aqueous solution is an emerging area of interest in supramolecular chemistry. The design of neutral architectures for anion recognition still remains a challenge. Among neutral anion receptor systems, urea and its derivatives are considered as privileged groups in supramolecular anion recognition, since they have two proximate polarized N-H bonds exploitable for anion recognition. Despite promising advancements in urea-based structures, the strong hydrogen bond drives detrimental self-association. Therefore, immobilizing urea fragments onto the rigid structures of a metal-organic framework (MOF) would prevent this self-association and promote hydrogen-bond-accepting substrate recognition. With this aim, we have synthesized two new urea-containing metal-organic frameworks, namely [Zn(bpdc)(L2)]nnDMF (TMU-67) and [Zn2(bdc)2(L2)2]n2nDMF (TMU-68) (bpdc = biphenyl-4,4′-dicarboxylate; bdc = terephthalate; L2 = 1,3-bis(pyridin-4-yl)urea), and we have assessed their recognition ability toward different anions in water. The two MOFs show good water stability and anion affinity, with a particular selectivity toward dihydrogen arsenate for TMU-67 and toward fluoride for TMU-68. Crystal structure characterizations reveal 3-fold and 2-fold interpenetrated 3D networks for TMU-67 and TMU-68, respectively, where all single interpenetrated networks are hydrogen bonded to each other in both cases. Despite the absence of self-quenching, the N-H urea bonds are tightly hydrogen bonded to the oxygen atoms of the dicarboxylate ligands and cannot be directly involved in the recognition process. The good performance in anion sensing and selectivity of the two MOFs can be ascribed to the network interpenetration that, shaping the void, creates monodimensional channels, decorated by exposed oxygen atom sites selective for arsenate sensing in TMU-67 and isolated cavities, covered by phenyl groups selective for fluoride recognition in TMU-68.
- Esrafili, Leili,Morsali, Ali,Hu, Mao-Lin,Azhdari Tehrani, Alireza,Carlucci, Lucia,Mercandelli, Pierluigi,Proserpio, Davide M.
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- Investigation of the anticancer activity of coordination-driven self-assembledtwo-dimensional ruthenium metalla-rectangle
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Coordination-driven self-assembly is an effective synthetic tool for the construction of spatially and electronically tunable supramolecular coordination complexes (SCCs), which are useful in various applications. Herein, we report the synthesis of a two-dimensional discrete metalla-rectangle [(η6-p-cymene)4Ru4(C6H2O4)2(2)2](CF3SO3)4 (3) by the reaction of a dinuclear half-sandwich ruthenium (II) complex [Ru2(η6-p-cymene)2(C6H2O4)Cl2] (1) and bis-pyridyl amide linker (2) in the presence of AgO3SCF3. This cationic ruthenium metalla-rectangle (3) has been isolated as its triflate salt and characterized by analytical techniques including elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy (1H-NMR), carbon nuclear magnetic resonance spectroscopy (13C-NMR), 1H-1H correlation spectroscopy (COSY), 1H-1H nuclear Overhauser effect spectroscopy (NOESY), diffusion ordered spectroscopy (DOSY), and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). Significantly, the 2D cationic ruthenium metalla-rectangle showed better anticancer activity towards three different cell lines (A549, Caki-1 and Lovo) as compared with the parent ruthenium complex (1) and the commercially used drug, cisplatin.
- Vardhan, Harsh,Nafady, Ayman,Al-Enizi, Abdullah M.,Khandker, Khalid,El-Sagher, Hussein M.,Verma, Gaurav,Acevedo-Duncan, Mildred,Alotaibi, Tawfiq M.,Ma, Shengqian
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- Moderate and advanced intramolecular proton transfer in urea-anion hydrogen-bonded complexes
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The study of the interactions of the three urea-based receptors AH, BH + and CH2+ with a variety of anions, in MeCN, has made it possible to verify the current view that hydrogen bonding is frozen proton transfer from the donor (the urea NH fragment in this case) to the acceptor (the anion X-). The poorly acidic, neutral receptor AH establishes two equivalent hydrogen bonds N-H...X-, with all anions, including CH3COO- and F-, in which moderate proton transfer from NH to the anion takes place. The strongly acidic, dicationic receptor CH2+ forms, with most anions, complexes in which two inequivalent hydrogen bonds are present: one involving moderate proton transfer (N-H...X-) and one in which advanced proton transfer has taken place, described as N-...HX. The degree of proton advancement is directly related to the basic tendencies of the anion. The cationic receptor BH+ of intermediate acidic properties only forms complexes with two inequivalent hydrogen bonds (moderate+advanced proton transfer) with CH 3COO- and F-, and complexes with two equivalent hydrogen bonds (moderate proton transfer) with all the other anions. Moreover, [B...HF] and [C...HF]+, on addition of a second F - ion, lose the bound HF molecule to give HF2-. Release of CH3COOH, with the formation of [CH 3COOH...CH3COO]-, also takes place with the [B...CH3COOH] complex in the presence of a large excess of anion. Copyright
- Baggi, Giorgio,Boiocchi, Massimo,Fabbrizzi, Luigi,Mosca, Lorenzo
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- The targeted design of dual-functional metal-organic frameworks (DF-MOFs) as highly efficient adsorbents for Hg2+ ions: Synthesis for purpose
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Designing adsorbents with accessible chelating sites and achieving high contaminant purification efficiency are still important to overcome environmental remediation challenges. As one of the significant global concerns, the presence of heavy metal ions i
- Esrafili, Leili,Gharib, Maniya,Morsali, Ali
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- Synthesis of unsymmetrical urea from aryl- or pyridyl carboxamides and aminopyridines using PhI(OAc)2via in situformation of aryl- or pyridyl isocyanates
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A tandem synthesis of unsymmetrical ureas (N-aryl-N′-pyridylurea andN,N′-bipyridylurea) from aryl- or pyridyl carboxamides and aminopyridinesviaHofmann rearrangement has been reported. In particular, benzamides, picolinamide, nicotinamide, and isonicotinamide generate reactive intermediate isocyanates,in situ, in the presence of PhI(OAc)2, which upon further reaction with aminopyridines form urea derivatives. As the formation of pyridylisocyanates from their corresponding carboxamidesviaHofmann rearrangement remained unexplored previously, attempts have been made to trap the isocyanates. While the three pyridylisocyanates were trapped as their corresponding carbamates, 3-pyridylisocyanate was isolated and characterized. Unlike closely related previous methods reported for urea synthesis, the current method avoids direct use of isocyanates or eliminates the use of toxic phosgene for thein situgeneration of isocyanates.
- Hunjan, Mandeep Kaur,Laha, Joydev K.,Singh, Neha
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p. 18815 - 18823
(2021/10/26)
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- Anchoring Drugs to a Zinc(II) Coordination Polymer Network: Exploiting Structural Rationale toward the Design of Metallogels for Drug-Delivery Applications
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A new series of coordination polymers (CPs) were synthesized and crystallographically characterized by single-crystal X-ray diffraction with the aim of developing drug-delivery systems via metallogel formation. Structural rationale was employed to design such coordination-polymer-based metallogels. As many as nine CPs were obtained by reacting two bis(pyridyl)urea ligands, namely, 1,3-dipyridin-3-ylurea (3U) and 1,3-dipyridin-4-ylurea (4U), and the sodium salt of various nonsteroidal antiinflammatory drugs, namely, ibuprofen (IBU), naproxen (NAP), fenoprofen (FEN), diclofenac (DIC), meclofenamic acid (MEC), mefenamic acid (MEF), and Zn(NO3)2. All of the CPs displayed 1D polymeric chains that were self-assembled through various hydrogen-bonding interactions involving the urea N-H and carboxylate O atoms and, in a few cases, lattice-occluded water molecules. The reacting components of the CPs produced five metallogels in dimethyl sulfoxide/water. The gels were characterized by rheology and transmission electron microscopy. Three selected metallogelators, namely, 3UMEFg, 3UNAPg, and 3UMECg, showed in vitro anticancer, cell imaging, and multidrug delivery for antibacterial applications, respectively. The shear-thinning properties of 3UMECg (rheoreversibility and injectability) make it a potential candidate for plausible topical application.
- Biswas, Protap,Dastidar, Parthasarathi
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supporting information
p. 3218 - 3231
(2021/03/01)
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- Progress in antischistosomal N,N′-diaryl urea SAR
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N,N′-Diaryl ureas have recently emerged as a new antischistosomal chemotype. We now describe physicochemical profiling, in vitro ADME, plasma exposure, and ex vivo and in vivo activities against Schistosoma mansoni for twenty new N,N′-diaryl ureas designed primarily to increase aqueous solubility, but also to maximize structural diversity. Replacement of one of the 4-fluoro-3-trifluoromethylphenyl substructures of lead N,N′-diaryl urea 1 with azaheterocycles and benzoic acids, benzamides, or benzonitriles decreased lipophilicity, and in most cases, increased aqueous solubility. There was no clear relationship between lipophilicity and metabolic stability, although all compounds with 3-trifluoromethyl-4-pyridyl substructures were metabolically stable. N,N′-diaryl ureas containing 4-fluoro-3-trifluoromethylphenyl, 3-trifluoromethyl-4-pyridyl, 2,2-difluorobenzodioxole, or 4-benzonitrile substructures had high activity against ex vivo S. mansoni and relatively low cytotoxicity. N,N-diaryl ureas with 3-trifluoromethyl-4-pyridyl and 2,2-difluorobenzodioxole substructures had the highest exposures whereas those with 4-fluoro-3-trifluoromethylphenyl substructures had the best in vivo antischistosomal activities. There was no direct correlation between compound exposure and in vivo activity.
- Wu, Jianbo,Wang, Chunkai,Leas, Derek,Vargas, Mireille,White, Karen L.,Shackleford, David M.,Chen, Gong,Sanford, Austin G.,Hemsley, Ryan M.,Davis, Paul H.,Dong, Yuxiang,Charman, Susan A.,Keiser, Jennifer,Vennerstrom, Jonathan L.
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supporting information
p. 244 - 248
(2018/01/10)
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- Urea Metal-Organic Frameworks for Nitro-Substituted Compounds Sensing
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Urea groups are known to form strong hydrogen bonds with molecules containing atom(s) that can act as hydrogen bond acceptor(s). Thus, urea is a particularly interesting building block for designing receptors for neutral or charged guests. In the quest for new sensors with enhanced performance for the detection of nitro-substituted compounds, two pillared metal-organic frameworks containing urea functional groups were synthesized and structurally characterized. The sensing properties of these frameworks toward nitro-analytes were investigated and compared to each other. The study clearly reveals the importance of urea groups orientation inside the pore cavity of MOFs, as well as the supramolecular interactions between the interpenetrated networks. This work is interesting as it represents the first example of urea-functionalized MOFs for nitro-analytes recognition.
- Azhdari Tehrani, Alireza,Esrafili, Leili,Abedi, Sedigheh,Morsali, Ali,Carlucci, Lucia,Proserpio, Davide M.,Wang, Jun,Junk, Peter C.,Liu, Tianfu
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supporting information
p. 1446 - 1454
(2017/02/15)
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- Lossen rearrangements under heck reaction conditions
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The classical Lossen rearrangement converts activated hydroxamic acids to isocyanates that form numerous products upon their reaction with nucleophiles. We report a simple and highly efficient method of using Heck reaction conditions to initiate Lossen rearrangements of hydroxamic acids. In addition, Lossen rearrangements occur in the presence of palladium(II) acetate or triethylamine, components of the Heck reaction, alone. A potential mechanism is provided to explain this reactivity and these results show that Heck reactions and Lossen rearrangements occur under the same conditions and may provide new methods for facile initiation of Lossen rearrangements.
- AbdelHafez, El-Shimaa M.N.,Aly, Omar M.,Abuo-Rahma, Gamal El-Din A.A.,King, S. Bruce
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supporting information
p. 3456 - 3464
(2015/02/05)
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- N-H...N(pyridyl) and N-H...O(urea) hydrogen bonding and molecular conformation of N-aryl-N′-pyridylureas
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Analysis of N-Ar-N′-4-pyridylureas (Ar = 4-X-phenyl, 4-py) crystal structures shows a gradual transition from urea...pyridyl N-H...N hydrogen bond in bifurcated synthon of R21 (6) graph set (X = H, Me, Cl) to single N-H...O and N-H...N hydrogen bonds in X = Br, I to urea N-H...O tape synthon (R21 (6) graph set) in N-phenyl-N′-tetrafluoropyridylurea. Thus the two extremes of urea pyridyl N-H...N synthon in N,N′-di(4-pyridyl) urea, N-H...O tape characteristic of diphenyl urea together with an in-between state are now visualized as snap shots in the solid-state. Most remarkably, molecular conformations too show a transition: the diaryl urea molecule is in the twisted metastable conformation in N-H...O tape structures, it is coplanar in the flat stable conformation for N-H...N structures, and one NH is in-plane while the other is oriented slightly outwards in the intermediate N-H...O and N-H...N hydrogen-bonded structure of N-4-Br-phenyl-N′-4-pyridylurea. Subtle and yet observable one-to-one molecular conformation to crystal structure systematic effects are analyzed. A one-dimensional zigzag chain in the crystal structure of N,N′-di(4-pyridyl) urea is consistent with the hydrogen bonding model for organic gelators.
- Chandran, Sreekanth K.,Nath, Naba K.,Cherukuvada, Suryanarayan,Nangia, Ashwini
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experimental part
p. 99 - 107
(2010/06/17)
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- CeCl3 · 7H2O-KI-catalyzed, environmentally friendly synthesis of N,N′-disubstituted ureas in water under microwave irradiation
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N,N′-Disubstituted ureas were efficiently synthesized by reactions of urea with a variety of amines in water under microwave irradiation using CeCl3 · 7H2O-KI as catalyst. This protocol has advantages of not using toxic phosgene and hazardous organic solvents, high reaction rate, high yield, and a simple workup procedure. Copyright Taylor & Francis, Inc.
- Li, Zheng
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p. 2325 - 2331
(2007/10/03)
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