Modification of naphthalene diimide (NDI) resulted in a photochemically stable, fluorescent 3,4,5-tris(dodecyloxy)benzamide derivative of NDI (TDBNDI), and introduction of the long alkyl chains endowed the compound with good compatibility with commonly found organic solvents and in particular superior self-assembly in the solution state. Further studies revealed that TDBNDI forms gels with nine of the 18 solvents tested at a concentration of 2.0% (w/v), and the critical gelation concentrations of five of the eight gels are lower than 1.0% (w/v), indicating the high efficiency of the compound as a low-molecular mass gelator (LMMG). Transmission electron microscopy, scanning electron microscopy, and confocal laser scanning microscopy studies revealed the networked fibrillar structure of the TDBNDI/methylcyclohexane (MCH) gel. On the basis of these findings, a fluorescent film was developed via simple spin-coating of the TDBNDI/MCH gel on a glass substrate surface. Fluorescence behavior and sensing performance studies demonstrated that this film is photochemically stable, and sensitive and selective to the presence of aniline vapor. Notably, the response is instantaneous, and the sensing process is fully and quickly reversible. This case study demonstrates that derivatization of photochemically stable fluorophores into LMMGs is a good strategy for developing high-performance fluorescent sensing films.
The
distribution of the constituents of a constitutional dynamic library
(CDL) may undergo time-dependent changes as a function of the kinetics
of the processes generating the CDL from its components. Thus, the
constitutional dynamic network (CDN) representing the connections
between the constituents changes from a kinetic distribution to the
thermodynamic one as a function of time. We investigated the behavior
of dynamic covalent libraries (DCLs) of four constituents generated
by reversible formation of CN bonds between four components,
2 aldehydes and 2 amino compounds, both in absence and in the presence
of metal cations. The associated [2 × 2] networks underwent time-dependent
changes from the initial kinetic distribution to the final thermodynamic
one, involving an orthogonal switch from one diagonal to the other
diagonal of the square [2 × 2] network leading to a very large
change in distribution. The DCL constituents could be switched from
kinetic products (imines) to thermodynamic products (oximes or acylhydrazones)
based on the reactivities of the components and the thermodynamic
stabilities of the constituents without addition of any external effector,
solely on the basis of the intrinsic properties of the self-contained
system. Such processes were achieved for purely organic DCLs/CDNs
as well as for inorganic ones containing two metal cations, the latter
changing from the silver(I) complex of an imine (kinetic product)
to the zinc(II) complex of a hydrazone (thermodynamic product). The
results bear relationship to out-of-equilibrium systems concerning
kinetic behavior in adaptive chemistry.
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