Recent advances in metallogels Tam, Anthony Yiu-Yan; Yam, Vivian Wing-Wah
Chemical Society reviews,
01/2013, Letnik:
42, Številka:
4
Journal Article
Recenzirano
Amongst the areas of supramolecular chemistry, low molecular weight gelators (supramolecular gels) have been considered to be one of the most interesting soft and smart materials due to their ability ...to construct polymeric structures from small molecules through non-covalent interactions. Recently, metal centres have been incorporated into organic-based gelators that can integrate the interesting and unique properties of metal complexes into gelator molecules that can hardly be achieved by pure organic compounds. In this review, we will give a summary of the recent developments on metallogels and their interesting properties originating from the metal centres.
Recently, metal centers have been incorporated into organic-based gelators that can integrate the interesting and unique properties of metal complexes into gelator molecules that can hardly be achieved by pure organic compounds. In this review, we will give a summary of the recent developments on metallogels and their interesting properties originating from the metal centres.
Effective antiviral therapy is important for tackling the coronavirus disease 2019 (COVID-19) pandemic. We assessed the efficacy and safety of combined interferon beta-1b, lopinavir–ritonavir, and ...ribavirin for treating patients with COVID-19.
This was a multicentre, prospective, open-label, randomised, phase 2 trial in adults with COVID-19 who were admitted to six hospitals in Hong Kong. Patients were randomly assigned (2:1) to a 14-day combination of lopinavir 400 mg and ritonavir 100 mg every 12 h, ribavirin 400 mg every 12 h, and three doses of 8 million international units of interferon beta-1b on alternate days (combination group) or to 14 days of lopinavir 400 mg and ritonavir 100 mg every 12 h (control group). The primary endpoint was the time to providing a nasopharyngeal swab negative for severe acute respiratory syndrome coronavirus 2 RT-PCR, and was done in the intention-to-treat population. The study is registered with ClinicalTrials.gov, NCT04276688.
Between Feb 10 and March 20, 2020, 127 patients were recruited; 86 were randomly assigned to the combination group and 41 were assigned to the control group. The median number of days from symptom onset to start of study treatment was 5 days (IQR 3–7). The combination group had a significantly shorter median time from start of study treatment to negative nasopharyngeal swab (7 days IQR 5–11) than the control group (12 days 8–15; hazard ratio 4·37 95% CI 1·86–10·24, p=0·0010). Adverse events included self-limited nausea and diarrhoea with no difference between the two groups. One patient in the control group discontinued lopinavir–ritonavir because of biochemical hepatitis. No patients died during the study.
Early triple antiviral therapy was safe and superior to lopinavir–ritonavir alone in alleviating symptoms and shortening the duration of viral shedding and hospital stay in patients with mild to moderate COVID-19. Future clinical study of a double antiviral therapy with interferon beta-1b as a backbone is warranted.
The Shaw-Foundation, Richard and Carol Yu, May Tam Mak Mei Yin, and Sanming Project of Medicine.
A new class of amphiphilic anionic platinum(II) bzimpy complexes has been demonstrated to show aggregation in water through Pt···Pt and π–π stacking interactions. An interesting aggregation–partial ...deaggregation–aggregation process and a morphological transformation from vesicles to nanofibers have been demonstrated. These changes can be systematically controlled by the variation of solvent composition and could readily be probed by UV–vis absorption, emission, NMR, transmission electron microscopy, and even with our naked eyes.
A series of polynuclear gold(I) sulfido complexes of bis(diphenylphosphino)amine ligands has been synthesized and characterized. A rather small variation in the conformation of the ...bis(diphenylphosphino)amine ligands has led to distinct differences in the identity of the polynuclear gold(I) sulfido complexes formed. Unprecedented concentration-dependent and solvation-dependent reversible cluster-to-cluster transformation between a dodecanuclear gold(I) sulfido complex (L Me -Au 12 ) and a hexanuclear gold(I) sulfido complex (L Me -Au 6 ) has been observed. The transformation process has been monitored not only by 1H and 31P{1H} NMR spectroscopy but also by UV–vis absorption spectroscopy and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) in the solution state. This work has provided a simple approach to achieve structure modulation of gold(I) sulfido complexes and an understanding of supramolecular transformations via external stimuli.
Stimuli-responsive structural transformation has attracted much attention for its potential to mimic the behavior of biological transformations and functions. Here, two unprecedented dodecanuclear ...and pentadecanuclear gold(I) sulfido clusters (denoted trans-Au 12 and trans-Au 15 , respectively) with impressive stimuli-responsive interconversion have been obtained by taking advantage of the judiciously designed tridentate phosphine ligand L trans as the building block. Both UV light and temperature can be applied to trigger the structural conversions between trans-Au 12 and trans-Au 15 . In addition, NMR, high-resolution electrospray ionization mass spectrometry, and UV–vis absorption spectroscopy have been employed to monitor the transformation process and decipher the mechanism of structural conversion. This work not only provides a paradigm to investigate photo-induced cluster-to-cluster transformation based on polydentate phosphine ligands but also offers a new direction for the construction of the stimuli-responsive materials.
Two unprecedented tetratriacontanuclear and tetraicosanuclear gold(I) sulfido clusters (denoted as Au 34 -L Me and Au 24 -L Cbz ) with different temperature-induced stimulus-responsive behavior and ...emission property have been constructed by taking advantage of the judiciously designed bidentate phosphine ligand. Au 34 -L Me represents the highest nuclearity of the gold(I) sulfido cluster with more than a thousand atoms in the molecule. Octagonal macrocycles based on metal-cluster nodes have been assembled for the first time. The self-assembly and temperature-induced stimulus-responsive processes were monitored by 1H and 31P{1H} NMR spectroscopy, and the identities of the discrete gold(I) complexes were established by single-crystal structural analysis and high-resolution electrospray ionization mass spectrometry data. The steric effects exerted by the substituents on the V-shaped 1,3-bis(diphenylphosphino)benzene ligand have been shown to govern the self-assembly from the 1D cluster and 3D cage to 2D macrocycles. This work not only offers a new strategy to construct and regulate the structure of 2D macrocyclic gold(I) sulfido complexes but also lays the foundation for the future precise design and controlled construction of higher polygonal and cluster-node macrocycles.
A series of alkynylplatinum(II) complexes of 2,6-bis(N-alkylbenzimidazol-2′-yl)pyridine has been synthesized and characterized by 1H NMR, IR, FAB mass spectrometry, and elemental analysis; the ...photophysical properties have also been investigated. All the complexes have been shown to exhibit interesting gelation properties. Scanning electron microscopy (SEM) of the xerogels showed a network of fibrous structures, typical of morphologies of organogels/metallogels. Interestingly, two of the complexes were found to show strong luminescence enhancement upon a gel-to-sol phase transition upon increasing the temperature. This unusual behavior is rarely encountered, as it represents a sharp contrast to that exhibited by other typical thermotropic organogels and metallogels reported so far. Variable-temperature UV−vis and luminescence spectroscopies were performed to probe the gel-to-sol phase transition. Concentration-dependent, variable-temperature, and time-resolved emission studies in dilute benzene solution have also been made to provide further insights into the spectroscopic origin in the sol forms. A quantitative treatment of the system based on the Birks scheme has been performed.
A series of platinum(II) terpyridine complexes with L‐valine‐modified alkynyl ligands has been synthesized. A complex with an unsubstituted terpyridine and one valine unit on the alkynyl is shown to ...be capable of gel formation, which is in sharp contrast to the gelation properties of the corresponding organic counterparts. Upon sol–gel transition, a drastic color change from yellow to red is observed, which is indicative of the involvement of Pt⋅⋅⋅Pt interactions. Through the concentration‐ and temperature‐dependent UV/Vis absorption, emission, circular dichroism, and 1H NMR studies, the contribution of hydrogen bonding, Pt⋅⋅⋅Pt and π–π stacking interactions as driving forces for gelation have been established, and the importance of maintaining a delicate balance between different intermolecular forces has also been illustrated.
Balancing act: Through the delicate balance of hydrogen bonding, Pt⋅⋅⋅Pt and π–π stacking interactions, the platinum(II) terpyridine complex with one amino acid unit on the alkynyl ligand shows drastic spectroscopic changes upon gelation (see figure, Boc=tert‐butoxycarbonyl).
Self-assembly of three-dimensional (3D) metallosupramolecular cages has drawn increasing attention for their potential to interconvert between different architectures due to the dynamic and ...reversible features of the coordination bond. These supramolecular transformations can provide unique approaches for the construction of stimuli-responsive supramolecular model systems to mimic biological transformation processes. While gold(I) clusters have attracted much interest due to their propensity to exhibit aurophilic interactions, the construction of 3D gold(I) cluster cages has remained a challenging and daunting task. Here, we proposed a “de-aurophilic” interaction strategy, which involves the prevention of aurophilic interaction formation between the basic (μ3-S)Au3+ units, to construct 3D gold(I) cluster cages. Through the judicious design of diphosphine ligands, an unprecedented class of gold(I) cluster cages with adaptive structures has been constructed. These gold(I) cluster cages are found to show intriguing stimuli-responsive structure transformation and interconversion. This work not only provides a strategy for the design and construction of novel 3D supramolecular cages based on cluster nodes but also offers a paradigm to study the stimuli-responsive structural interconversion between the unique structures of these gold(I) cluster cages.
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