N-Heterocyclic carbene–silver complexes: A new class of antibiotics

Kascatan-Nebioglu, Aysegul; Panzner, Matthew J.; Tessier, Claire A.; Cannon, Carolyn L.; Youngs, Wiley J.

doi:10.1016/j.ccr.2006.08.019

Cited by 452 publications

(258 citation statements)

References 80 publications

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“…There have been previous examples of stimuli-responsive molecular cages (41,61) and baskets (45)(46)(47)(48)(49)(50)(51)(52)62) for targeted delivery; however, most of the systems lack the spontaneous spectral or other kinds of responses to facilitate instant signal detection. In contrast, the guest release and capture processes of the current molecular rectangles are capable of being probed by UV-vis absorption and emission titration studies.…”

Section: Resultsmentioning

confidence: 99%

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Chan

Lam

Tanaka

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

120

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A series of multiaddressable platinum(II) molecular rectangles with different rigidities and cavity sizes has been synthesized by endcapping the U-shaped diplatinum(II) terpyridine moiety with various bisalkynyl ligands. The studies of the host-guest association with various square planar platinum(II), palladium(II), and gold(III) complexes and the related low-dimensional gold(I) complexes, most of which are potential anticancer therapeutics, have been performed. Excellent guest confinement and selectivity of the rectangular architecture have been shown. Introduction of pH-responsive functionalities to the ligand backbone generates multifunctional molecular rectangles that exhibit reversible guest release and capture on the addition of acids and bases, indicating their potential in controlled therapeutics delivery on pH modulation. The reversible host-guest interactions are found to be strongly perturbed by metal-metal and π-π interactions and to a certain extent, electrostatic interactions, giving rise to various spectroscopic changes depending on the nature of the guest molecules. Their binding mode and thermodynamic parameters have been determined by 2D NMR and van't Hoff analysis and supported by computational study. noncovalent interactions | platinum complex | luminescence T he study of metal-metal interactions has drawn enormous attention since the past two decades because of the intriguing spectroscopic and photophysical properties arising from the close proximity of the metal centers (1, 2). Square planar d 8 platinum(II) complexes with coordination unsaturation are one of the important classes of metal complexes that have been extensively explored because of their capability to exhibit metalmetal interactions and display rich photophysical properties (3-26). Platinum(II) terpyridine complexes have been found to exhibit rich polymorphism in the solid state (16)(17)(18)(19)(20) owing to their square planar coordination geometry, which permits facile access to Pt(II)···Pt(II) interactions as well as π-π interactions between the chromophores. It was not until 2001 that the first successful synthesis of platinum(II) terpyridine alkynyl complexes, which possess enhanced solubility and luminescence compared with the chloro counterpart, was reported (16). Additional efforts have been devoted to the use of the system to respond to external stimuli, such as variation in solvent composition (17, 18), pH (19, 20), temperature (21, 22), addition of ionic (24-26), and polymeric species (27,28), in which spectral changes induced by strong Pt(II)···Pt(II) and π−π interactions have been displayed.In the past few decades, enormous efforts have been devoted to the construction of molecular architectures by fusing the organic framework to the transition metal centers through selfassembly processes (29-57). There has been continuous interest in the construction of stimuli-responsive metallosupramolecular architectures with diverse sizes, shapes, and symmetries to rationalize the criteria for molecular recognition and impa...

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Section: Resultsmentioning

confidence: 99%

Multiaddressable molecular rectangles with reversible host–guest interactions: Modulation of pH-controlled guest release and capture

Chan

Lam

Tanaka

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

120

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“…transesterification, nucleophilic aromatic substitution, and cycloaddition chemistry). 4 Some of the latest developments in carbene chemistry include their use in highly specific functions such as antimicrobial agents 5 and in liquid crystals, 6 and further investigations will undoubtedly reveal many more fascinating and useful applications for these systems as a whole.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structures of Main-Group Carbene Analogues

et al. 2007

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The electronic structures of fifteen Group 13-16 carbene analogues are analyzed using various quantum chemical methods and compared to the data obtained for the parent N-heterocylic carbene (NHC), imidazol-2-ylidene. The results of this study present a uniform analysis of the similarities and differences in the electronic structures of p-block main group carbene analogues. Though all systems are formally isovalent, the theoretical analyses unambiguously indicate that their electronic structures run the gamut from C=C localized (Group 13) to C=N localized (Group 16) via intermediate, more delocalized, systems. In particular, neither the stibenium ion nor any of the chalcogenium dications is a direct analogue of imidazol-2-ylidene as they all contain two lone pairs of electrons around the divalent main group center, instead of the expected one. The reason behind the gradual change in the electronic structure of main group analogues of imidazol-2-ylidene was traced to the total charge of the systems, which changes from anionic to dicationic when moving from left to right in the periodic table. Results from theoretical analyses of aromaticity show that all Group 13-16 analogues of imidazol-2-ylidene display some degree of aromatic character. The heavier Group 13 anions benefit the least from π-electron delocalization, whereas the cationic Group 15 systems are on par with the parent carbon system and display only slightly less aromatic character than cyclopentadienide, a true 6π-electron aromatic species. The σ-donor and π-acceptor ability of the different main group carbene analogues is also evaluated.

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“…After the initial burst of research in the catalysis area, use of NHC metal complexes in other areas gained attention and is still developing, especially in biological and medicinal chemistry. For example, various NHC metal complexes have been shown to possess anti-infective activities (e.g., many Ag NHC complexes [3]), anti-biotic activities [4] and anti-cancer activities (e.g. some complexes of Ag, Pd, Au, Pt, Ru and other metals) [5][6][7].…”

Section: Introductionmentioning

confidence: 99%