The First Example of Bisindole-Based Polyurethane Dendrimers: Synthesis and Performance in DSSC

Tuning anion binding properties of Bis(indolyl)methane Receptors: Effect of substitutions on optical responses

Chromogenic probes based onoxidizedbis(indolyl)methanes have been synthesized with varying substituents (R = -Me [1], -OMe [2], -OH, [3]) on the central aryl ring. In addition to electronic influence, the involvement of substituents in ion-dipole and charge-assisted hydrogen bonding interactions significantly alters the solvatochromic response and pH-sensitive behavior. In polar aprotic solvents, like CH₃CN, a concentration-dependent stepwise color change was observed with F^- ions. In the case of2, a reversible hydrogen bonding interaction between the deprotonated probe and HF₂^- dimer might be responsible for that, while step-wise deprotonation caused by F^- ions could be the probable reason with3. Since the formation of HF₂^- is energetically unfavorable in a polar protic solvent, the response of 2 with F^- ions appears to be very different in EtOH medium. Interestingly, no such alteration in anion sensing behavior was noticed with3going from an aprotic to a protic solvent.

Thiol-Ene Click-Inspired Late-Stage Modification of Long-Chain Polyurethane Dendrimers

The construction of well-defined polyurethane dendrimers is challenging due to the high reactivity of externally added or in situ formed isocyanates leading to the formation of side products. With a primary focus of dendrimer research being the interaction of the periphery and the core, we report the synthesis of a common polyurethane dendron, which allows for the late-stage variation of both the periphery and the core. The periphery can be varied simply by installing a clickable unit in the dendron and then attaching to the core and vice-versa. Thus, a common dendron allows for varying periphery and core in the final two steps. To accomplish this, a protecting group-free, one-pot multicomponent Curtius reaction was utilized to afford a robust and versatile AB2 type polyurethane dendron employing commercially available simple molecules: 5-hydroxyisophthalic acid, 11-bromoundecanol, and 4-penten-1-ol. Subsequent late-stage modifications of either dendrons or dendrimers via a thiol-ene click reaction gave surface-functionalized alternating aromatic-aliphatic polyurethane homodendrimers to generation-three (G3). The dendrons and the dendrimers were characterized by NMR, mass spectrometry, and FT-IR analysis. A bifunctional AB2 type dendritic monomer demonstrated this approach’s versatility that can either undergo a thiol-ene click or attachment to the core. This approach enables the incorporation of functionalities at the periphery and the core that may not withstand the dendrimer growth for the synthesis of polyurethane dendrimers and other dendritic macromolecules.

The impact of metal coordination on the assembly of bis(indolyl)methane-naphthalene-diimide amphiphiles

The self-assembly and coordination of amphiphiles comprised of naphthalenediimide (NDI) and bis(indolyl)methane (BIM) chromophores were investigated as a function of pH and metal. As observed by TEM, SEM and AFM imaging, the self-assembly of NDI-BIM 1 produced irregular nanostructures at neutral pH in CH3CN-H2O (1 : 1); whereas, well-defined nanotubes were observed at pH 2. Conversely, Fmoc-protected, NDI-BIM 2 formed nanotubes at neutral pH and nonspecific aggregates at pH 2. Upon coordination of Cu2+ ions to the bis(indoyl)methane moiety, a reorganization from nanotubes to vesicular structures was observed.

Cyclohexadienone core 3,6-di-tert-butylcarbazole decorated triazole bridged dendrimers: synthesis, photophysical and electrochemical properties and application as an additive in dye-sensitized solar cells

An enhanced efficiency of 9.01% was realized for G₂ dendrimer based DSSC.