Segregation of Constitutional Isomers of Some Aromatic Amines Exploiting the Changes of Photo‐Luminescence Behaviour of Isoreticular Metal‐Organic Frameworks.

Three different two dimensional Cd(II)‐based metal−organic frameworks (MOFs) have been synthesized by utilizing same N,N′‐donor ligand and three different functionalized dicarboxylate linkers namely isophthalate, 5‐nitroisophthalate and 5‐hydroxyisophthalate for compound 1, 2 and 3 respectively. The compounds that are isoreticular bi‐walled 2D frameworks, show dual fluorescence emission spectra for their π‐π* and n‐π* excitation. Compound 1 is consists of unsubstituted bridging isophthalate whereas 2 and 3 are made with bridging isophthalate that are substituted by electron withdrawing –NO2 group and electron donating –OH group respectively. These different electronic environments in three MOFs are found effective to respond differently towards the constitutional isomers of aromatic amines having suitable electronic environment. Compound 1 responses towards non‐polar –CH2 group containing picolylamine moieties, showing maximum fluorescence emission enhancement for 2‐picolylamine in comparison to 3‐ and 4‐ isomer of picolylamine derivates. Compound 2, consisting electron withdrawing –NO2 group, responses more significantly towards the electron rich phenylenediamines showing maximum quenching in case of m‐phenylenediamine compared to their ortho and para isomers. The change of functionalisation from –NO2 to –OH in 3, helps to detect the electron deficient aminopyridines; where the maximum fluorescence quenching has been observed in presence of 3‐aminopyridine in contrast to its other isomers. [ABSTRACT FROM AUTHOR]