Novel Fluorene Based Host Compounds Designed to Probe Solid-State Fluorescence

Abstract

Two novel host compounds, 2,7-bis(3-hydroxy-3,3-diphenylprop-1-ynyl)fluorene and 2,7-bis [3,3-(biphenyl-2,2 0 -diyl)-3-hydroxyprop-1-ynyl]fluorene have been synthesized. Many inclusion complexes of these host compounds with common volatile guests show solid-state fluorescence, which is ascribed to the existence of rigid dimers in the crystal structures, allowing excimer formation. Differential intermolecular interactions about the fluorescent moiety result in various colored emissions.Guest specific fluorescence in solution is frequently used in sensing applications, 1 but solid-state fluorescence in host:guest complexes is rarer. Host complexes or sensors have been designed to respond selectively to specific organic analytes 2 (though fluorescence quenching, rather than enhancement, is more frequent in such applications 3 ). Recently, fluorescence due to toluene inclusion in crystals of disubstituted anthracenes 4 has been reported and we have previously noted guest specific solid-state fluorescence in crystalline inclusion complexes of 2,7-bis(3-hydroxy-3,3-diphenylprop-1-ynyl)fluoren-9-one (1).5 Analysis of molecular packing in the crystalline state led to the suggestion that emission was occurring from dimers that formed excimers due to the interactions of close stacked systems. Also of importance was the absence of strong intermolecular interactions (such as hydrogen bonds) to the fluorescent fluorenone core as these would allow radiationless decay to occur in analogous fashion to solution phase hydrogen-bond donors.5b To test this hypothesis, we have synthesized two new hosts, 2,7-bis(3-hydroxy-3,3-diphenylprop-1-ynyl)fluorene (2a) and 2,7-bis [3,3-(biphenyl-2,2 0 -diyl)-3-hydroxyprop-1-ynyl]fluorene (2b) as shown in Scheme 1, and have screened a range of inclusion complexes for the onset of fluorescence.Crystallographic investigations, used to probe intermolecular interactions in the solid state, provide a basis for explaining the source of solid state fluorescence and changes in emission max . ExperimentalPreparation of 2a. 2,7-Dibromofluorene (2.0 g, 6.2 mmol),

Violet‐to‐Blue Tunable Emission of Aryl‐Substituted Dispirofluorene–Indenofluorene Isomers by Conformationally‐Controllable Intramolecular Excimer Formation

“…This has been supported by theoretical modeling (see below). The bulkiness of the substituents borne by the aryl rings play hence a crucial role in the tuning of the emission color of aryl‐substituted 2 c – g 55. Such remarkable tuning of the emission band by steric hindrance appears to be a simple and efficient way to tune the emission colors of aryl‐substituted DSF‐IFs 2 fluorophores.…”

π–π Stacking and ferromagnetic coupling mechanism on a binuclear Cu(ii) complex

“…For example, the p-p stacking interaction resulted in a silver complex displaying a highly electrical conducting behaviour, 34 and it also led to a change in the fluorescent emission intensity for some compounds. 35 In the area of magnetic coupling interactions, p-p stacking interaction also plays an important role. For example, some authors attributed the strong ferromagnetic order to p-p stacking interaction, 36 and other authors found the p-p stacking interaction led to a strong antiferromagnetic interaction between spin-carriers.…”

The magnetic study of a binuclear Cu(ii) complex with π–π stacking interactions

“…For example, the p-p stacking interaction resulted in a silver complex displaying a highly electrical conducting behaviour, 34 and it also led to a change in the fluorescent emission intensity for some compounds. 35 In the magnetic coupling area, some authors attributed the strong ferromagnetic order to p-p stacking, 36 and other authors found the p-p stacking interaction led to a strong antiferromagnetic interaction between mononu-clear Ni(II) complexes. 37 In a word, the p-p stacking interaction should be one of the key factors that dominate magnetic coupling, but neither a fitting formula nor theoretical calculations have been reported for the magnetic coupling of a p-p stacking interaction system as yet.…”