Fundamental Aspects of Xanthene Dye Aggregation on the Surfaces of Nanocluster Polyoxometalates: H‐ to J‐Aggregate Switching

Abstract

The induced aggregation of the xanthenedye rho-damineB (RhB) on metal oxide centers belonging to the highly symmetric surfaces of precise nanoscale templates with Keplerate (Mo 132 )o rtoroidal (Mo 138 )s tructures has been studied. With the joint use of the Langmuir isotherma nd full Stern-Volmer models, the thermodynamic reasons for dye adsorption on the nanocluster surface, such as amixture of monomer,H -aggregate (H-dimer), and J-aggregate forms (which can coexist or switch one into another under the exact conditions), were established:t his was shown through UV/Vis and fluorescence spectroscopies. By using the frame-work of the excitonm odel, it is shownt hat the angle( a)b etweent he transition dipole moments of RhB is very sensitive to surface strain inside the dye sub-monolayer.A saresult, it is possible to switch from H-to J-aggregates by the postfunctionalization of polyoxometalate (POM)-RhB associates by the surfactant bilayer shell, which allows the surface strain to grow.R ecommendations are provided for managing the appearance of H-or J-aggregates on metal oxide (or polyelectrolyte) surfacesd uring photovoltaico rb ioimaging applications.[a] V. Fazylova, N. Shevtsev,S .M ikhailov, Prof. [b] G. Kim Institute of Organic Synthesis Ural Branch of the Russian Academyo fSciences 22 AkademicheskayaS t.,6 20990 Ekaterinburg (Russia) Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Physicochemical and biochemical properties of the Keplerate-type nanocluster polyoxomolybdates as promising components for biomedical use

“…An integrated approach to the study of the physicochemical properties of the Mo 132 and Mo 72 Fe 30 Keplerate POMs [138,161,301], as well as the possibility of their association with bioactive molecules and fluorescent dyes, made it possible to formulate the concepts [302][303][304] of creating long-time-drug-releasing systems (LDRS) with a function LDRS will be based on the release of molecules of bioactive (medicinal) substances, initially bound with POM, and the intensification of fluorescent labels luminescence. The release occurs at the normal pH (7.2-7.4) of the body environment, due to the POM destruction.…”

“…The release occurs at the normal pH (7.2-7.4) of the body environment, due to the POM destruction. The main principle LDRS are based on is the discovered effect [302][303][304] of a fluorescent label (xanthene dye rhodamine-B, RhB) inactivation on the POM surface due to charge transfer processes. This makes it possible to monitor the drugs release due to the intensification of the signal from the fluorescent labels [305,306] incorported in the applied LDRS.…”

“…In [307], it was found that RhB, chosen from a number of xanthene dyes, is characterized by the concentration quenching of luminescence due to a static mechanism, i.e., formation of non-luminescent H-aggregates. It was shown in [304] that the reason for the RhB fluorescence quenching in an associate with POM is the photoinduced charge transfer from the level of the lowest unoccupied molecular orbital (LUMO) of the donor (RhB) to the LUMO level of the acceptor (POM). According to the cyclic voltammetry data [308,309], the LUMO level of RhB is 0.65 eV higher than the LUMO level of POM, which leads to the spontaneous electron transfer from RhB to POM in an excited state and formation of the RhB+/Mo n− 132 ionic pair.…”

A Self‐locked β‐Cyclodextrin‐rhodamine B Spirolactam with Photoswitching Properties

“…[32] In contrast, the non-symmetrical J aggregates are fluorescent and absorb at ~570 nm, whereas the monomers absorb near ~550 nm. [32,33] The aqueous solution of the βCD/Rho complex at alkaline pH is red-colored and visibly fluorescent. Specifically, at the present working pH ~9.5, the βCD/Rho complex in water with 2 eq of NMM shows strong absorption in the visible region (λ max = 555 nm, Figure S10).…”

The precise modification of a nanoscaled Keplerate-type polyoxometalate with NH2-groups: reactive sites, mechanisms and dye conjugation

“…templates) for the supramolecular design of functional materials. 2,3 Due to electrostatic forces, hydrogen bonding, van der Waals interactions and ligand exchange, 4 a POM's surface can be flexibly tuned with a variety of organic molecules to produce hybrids for different applications: porphyrin-sensitized hydrogen evolution, 5 "metal-oxide/dye" interface modeling, 2,6 NO donors, 7 drug release, [8][9][10] selective membranes, 11 magnetic nano-capsules, 12 contrast agents for magnetic resonance imaging (MRI), 13 liquid crystal design, 14 "host-in-host" supramolecular core-shell-type systems with cyclodextrins 15 and superlattice formation. 3 Furthermore, a recent study on the influence of the cooperative phenomenon on volatile molecule sorption into giant POMs showed that they can be used as nanoscaled molecular-separating units.…”