A rationally designed probe L, which consists of both cation and anion binding sites, is capable of displaying interesting aggregation induced emission (AIE) properties. L not only can sense Al(3+) and Zn(2+) through selective turn-on fluorescence responses in 9 : 1 methanol-HEPES buffer (5 mM, pH 7.3; 9 : 1, v/v) medium due to metal ion triggered AIE activity, but also can distinguish them through individual emission signals. L can also detect Cu(2+) in mixed buffer medium and F(-) in acetonitrile through sharp colorimetric responses. All the sensing processes are conspicuous through the naked eye. A theoretical study strongly backed the proposed sensing mechanisms.

Here we report the synthesis and structural characterizations of a new 3D functional metal−organic framework {[K 8 (PTC) 2 (H 2 O) 1.5 ]·4H 2 O} n formed by the self-assembly of K I and chromophoric linker perylenetetracarboxylate (PTC). The structure determination shows a 3D pillared-layer framework, where perylene cores are arranged in an unusual end-to-end off-slipped and zigzag arrangement directed by K I −carboxylate bonding. Photophysical studies revealed a broad absorption band with λ max of 531 nm and bathochromically shifted red emission centered at 655 nm. This characteristic emission has been assigned due to Jcoupling of the PTC linkers in the solid state. The framework contains 1D water-filled channel, and the desolvated framework shows permanent porosity, "as realized by type-I CO 2 adsorption profile at 195 K. Interestingly, the guest and coordinated water molecules in the framework are connected via H-bonding and based on these characteristics, the framework was further exploited for proton conduction. It shows remarkable conductivity of 1 × 10 −3 S cm −1 under ambient conditions (98% RH) with low activation energy. ■ INTRODUCTIONOrganic chromophores with polyaromatic cores have attracted great attention due to their potential applications in lightemitting diode (LED) and photovoltaics (PV) and as bio/ chemo sensors and molecular-conducting materials; 1−5 however, such chromophoric molecules with remarkable photostability and high quantum yield preferably form sandwich-type H-aggregates, which exhibit sufficiently quenched fluorescence due to delocalized excitons or excimer formation. 6−11 Thus, various optoelectronic materials based on J-aggregation of the chromophores have been designed and developed. 12,13 The slipped arrangement of the chromophores, that is, J-type aggregation, leads to a bathochromic shift of the absorption band and also higher exciton mobility, which is important for light-harvesting application. 7 To date, fluorescent J-aggregates have been mainly studied on organic supramolecular assembly of several polyaromatic chromophores (e.g., substituted perylene/naphthalenebisimide, cyanine, squaraine dyes) extended via various noncovalent interactions; 6−11 however, such studies on inorganic−organic hybrid assemblies like in metal− organic frameworks (MOFs) are underexplored. 14 We envisage that the coordination-driven slipped arrangement of chromophoric linker could be another approach for designing fluorescent MOF based on J-aggregation. Such metal-directed J-aggregation of the chromophores is observed in natural lightharvesting pigment chlorophyll. 8−11 In addition, coordinationdriven spatial organization of chromophores appears to be advantageous because such hybrid assemblies would exhibit interesting optoelectronic properties coupled to enhanced thermal and mechanical properties. 15 Furthermore, the recent upsurge in design and synthesis of proton conductive MOFs stemmed from their potential use in electrochemical devices such as fuel cells, sensors, and so on. 16−23 In partic...

No abstract