A Fluorescent, Shape-Persistent Dendritic Host with Photoswitchable Guest Encapsulation and Intramolecular Energy Transfer

Abstract

A fluorescent and photoresponsive host based on rigid polyphenylene dendrimers (PPDs) has been synthesized. The key building block for the divergent dendrimer buildup is a complex tetracyclone 12 containing azobenzenyl, pyridyl, and ethynyl entities. The rigidity of polyphenylenes is of crucial importance for a site-specific placement of different functions: eight azobenzene (AB) moieties into the rigid scaffold, a fluorescent perylenetetracarboxdiimide (PDI) into the core, and eight pyridin functions into the interior cavities. AB moieties of host-1 undergo reversible cis-trans photoisomerization and are photostable, as confirmed by various techniques: UV-vis, (1)H NMR, size exclusion chromatography, and fluorescence correlation (FCS). In this system, AB moieties act as photoswitchable hinges and enable control over (i) molecular size, (ii) intramolecular energy transfer between AB and PDI, and (iii) encapsulation and release of guest molecules. The presence of PDI allows not only following the effect of cis-trans photoisomerization on molecular size with highly sensitive FCS but also monitoring the efficiency of the intramolecular energy transfer process (from AB to PDI) by time-resolved optical spectroscopy. Pyridyl functions were incorporated to facilitate guest uptake via hydrogen bonds between the host and guests. Also, we have demonstrated that the photoswitchability of the host can be utilized to actively encapsulate guest molecules into its interior cavities. This novel, light-driven encapsulation mechanism could enable the design of new drug delivery systems.

Accurate Diffusion Coefficients of Organosoluble Reference Dyes in Organic Media Measured by Dual-Focus Fluorescence Correlation Spectroscopy

“…This procedure was also used in chloroform and o-dichlorobenzene. 59, 66 Koynov et al measured the Stokes radius of commercially available, fluorescently labeled silica nanoparticles in DMSO by DLS, and used this value to calibrate their FCS setup. 49 The drawbacks of the mentioned methods are obvious.…”

Light‐Orchestrated Macromolecular “Accordions”: Reversible Photoinduced Shrinking of Rigid‐Rod Polymers

“…Their direct use in solution, immobilized at surfaces, or integrated into adequate matrices, allow for the elaboration of nano-carriers, [1] molecular electronic memory circuits, [2] adaptive systems, [3] artificial muscles, [4] or healable materials, [5] among others. In nature, lightinduced geometrical modifications of molecular systems [10] lead to primary biological functions, such as the visual perception in vertebrates, [11] or proton pumping in some bacteria, [12] two examples that nicely illustrate the potential of photo-inducing structural modifications in organic systems.Changing the geometry of macromolecules can be exploited for the elaboration of guest-encapsulation structures, [13] and opto-mechanical materials, [14] which enable direct conversion of photon energy into mechanical work. Of particular interest are switches controlled by non-invasive triggers, especially light, which can display high spatial and temporal resolution.…”

“…Changing the geometry of macromolecules can be exploited for the elaboration of guest-encapsulation structures, [13] and opto-mechanical materials, [14] which enable direct conversion of photon energy into mechanical work.…”

“…Photoswitches [7] were used to change properties, such as conductance [8] and basicity, [9] based on light-induced alteration of the molecular geometry, that is, their dimensions and shape. In nature, lightinduced geometrical modifications of molecular systems [10] lead to primary biological functions, such as the visual perception in vertebrates, [11] or proton pumping in some bacteria, [12] two examples that nicely illustrate the potential of photo-inducing structural modifications in organic systems.Changing the geometry of macromolecules can be exploited for the elaboration of guest-encapsulation structures, [13] and opto-mechanical materials, [14] which enable direct conversion of photon energy into mechanical work. To prepare efficient structures and materials however, it is desirable to design macromolecules apt to dramatically change shape and dimensions upon exposure to light.…”

Synthesis and properties of template-promoted switchable dithienylethene-based macrocycles

“…In recent decades, macrocyclic chemistry has been developed into a major field of supramolecular chemistry due to its important role playing in host-guest chemistry [1][2][3][4], supramolecular self-assembly [5,6] and so on [7]. Macrocyclic structures with shaped-persistent have been largely synthesized, especially in fully p-conjugated backbones, and have been used in the field of material science.…”