Abstract
A meso-functionalization strategy has successfully been applied to the synthesis of novel 1,3,7-triazapyrene derivatives of calixarenes. The key synthetic step in these transformations providing the direct C–C bond formation is nucleophilic substitution of hydrogen (SNH) in 1,3,7-triazapyrene. General photophysical characteristics for these macrocyclic compounds, as well as features in emission properties upon addition of various metal cations have been elaborated. Studies using NMR spectroscopy have also shown a mutual effect of both calix[4]arene and 1,3,7-triazapyrene moieties on the coordination process. The complex stoichiometry and binding constants for Al3+ and Fe3+ guests have been explored with titration experiments.
Highlights
Iron is an important microelement that plays a key role in the metabolism, synthesis of DNA and RNA,5 it provides the ability of haem to transfer oxygen
In order to synthesize the desired 1,3,7-triazapyren-6-yl derivatives of calix[4]arenes, a meso-functionalization strategy including a series of subsequent transformations, such as protection of the hydroxy group, bridge-lithiation, followed by nucleophilic substitution of hydrogen (SNH) in 1,3,7-triazapyrene, oxidation of the sH-adducts, and nal deprotection has successfully been applied in this study (Scheme 1)
It should be emphasized that the exploited reactions of nucleophilic substitution of hydrogen (SNH) are considered as environmentally benign PASE (Pot, Atom, Step Economy) methodology,16 enabling the direct C–H functionalization of aromatics,17 as well as non-aromatic azaheterocyclic substrates
Summary
The design of organic molecules for selective detection of biologically and environmentally important analytes, such as small molecules and metal ions attracts a considerable attention from the broad scienti c community.1 Among a variety of metal ions, Al3+ and Fe3+ are known to be of great importance due to a wide range of practical applications in machinery, aviation, electronic devices, and daily life.2 Aluminum-containing substances are well-spread in food additives and water treatment systems.3 It is worth noting that accumulation of aluminum in living system turns out to cause anemia and pathology of the nervous system, e.g., Alzheimer disease.4 Besides, iron is an important microelement that plays a key role in the metabolism, synthesis of DNA and RNA,5 it provides the ability of haem to transfer oxygen.6 On the one hand, the lack of Fe3+ ions results in hemochromatosis, liver injury, Parkinson's disease, and cancer. In order to synthesize the desired 1,3,7-triazapyren-6-yl derivatives of calix[4]arenes, a meso-functionalization strategy including a series of subsequent transformations, such as protection of the hydroxy group, bridge-lithiation, followed by nucleophilic substitution of hydrogen (SNH) in 1,3,7-triazapyrene, oxidation of the sH-adducts, and nal deprotection has successfully been applied in this study (Scheme 1).
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