Lumophore-spacer-receptor

LUMOPHORE-SPACER-RECEPTOR SYSTEMS (NORMAL LOGIC)... 

The switching efficiency of lumophore-spacer-receptor systems can be improved by using multiple receptor modules. The PET rate is increased in the device when free of guest ions since more than one site can provide the transiting electron. The simplest cases, such as 4, are those where the receptor units are well separated to prevent interdependent ion binding with an interposed lumophore to minimize the lumophore-receptor spacing for maximum PET rates. Besides this statistical effect, receptors may also cooperatively participate in PET. This may be the case in 5 and 6. ... 

Lumophore-spacer-receptor systems are not by any means limited to the ami-noalkyl aromatic family even if we focus on the receptor unit. Still, the latter family is likely to remain a major provider of ionically switchable luminescent devices. Aminoalkyl aromatics also serve as the platform for the development of luminescent PET sensors for a whole class of nonionic saccharides. While aliphatic amines, either singly or in arrays, can serve as receptors for a variety of cationic... 

Shinkai s 38 is also a PET system whose fluorescence is controlled by Na" binding to a coordinatively active spacer which is a calix[4]aiene tetraester in this case. However, the through-space distance between the photoactive termini is expanded by Na complexation, thus reducing the PET efficiency. Kuhn s 39 is not dissimilar in that a PET-type quencher (a nitroaromatic unit) is held away from the lumophore by Ca binding. However a conventional lumophore-spacer-receptor is also contained within 39 as found in 24. At this point it would not be out of place to mention several important studies on the control of PET/EET by ion binding to a coordinatively active spacer between photoactive terminii." " System 36 is structurally related to Verhoewen s 40 since they both contain an aromatic lumophore and an aromatic amine with one or more interposed aliphatic amines. System 40 also displays the functional similarities that PET processes were... 

LUMOPHORE-SPACER-RECEPTOR SYSTEMS WITH REDOX ACTIVE GUESTS... 

Cu(II) is one of the best examples of a redox active guest, but apparently not when it is imprisoned in a cryptand such as 53. In this case, the Cu(II) is silent over a wide potential range during cyclic voltammetry. System 53 is designed as a lumophore-spacer-receptor system such as 28-30 and 33-34 in Section 1 with multiple lumophores. It also shows similar luminescence off-on switching with and even with Cu(II). The possibility of Cu(II) induced production of from moisture appears to have been ruled out. The absence of EET is a mystery which can only be dispelled by further studies on this interesting system. 

LUMOPHORE,-SPACER,-RECEPTOR-SPACER2-LUMOPHORE2 SYSTEMS... 

The fact that 1 is fronting a host of molecular lumophore-spacer-receptor PET signaling systems appealed to Tusa, Leiner, and their collaborators at AVL Biosense Corporation, Atlanta, and Graz, Austria. Related sensory molecules now lie at the heart of blood electrolyte measurement in critical care units in hospitals [52], This is perhaps the clearest endorsement to date of the device capability of luminescent PET signaling systems. 

An early report [57] from Michael Schuster and his team at the Technical University of Munich, Germany highlighted the lumophore-spacer-receptor system 13 which showed strong fluorescence recovery with intrinsic quenchers... 

Schuster et al. s latest effort [61]—a clear PET system of the lumophore-spacer-receptor format—breaks free from this quenching mold just like their 1993 case [57], Sensor 17 is capable of binding (through the S atom to Cu2+ or... 

But the bulk of results have emerged from Shinkai s laboratories [178] in Fukuoka and Kurume, Japan. His prototypical example, 24, is essentially a classical aminomethylaromatic lumophore-spacer-receptor system with a twist that the weak B-N bond allows rather rapid PET from the amine unit to the anthracene resulting in weak fluorescence [176], The binding of glucose to produce the boronate ester leads to a much stronger B-N bond that arrests the PET process and produces a large fluorescence enhancement. 

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