Crystal engineering of Pb(II)-salen coordination polymer enforced for the selective fluorescence NACs sensing activity in a dispersed aqueous medium: A combined experimental and theoretical DFT monologue

A new 1D coordination polymer (CP), [(SCN)Cd(L-1)Pb(NCS)](n) (1) was synthesized using N2O4-based Scaffold (H2L1 = N, N' -bis(3-methoxysalicylidenimino)-1,3-diaminopropane) and structurally characterized using various analytical instruments. X-ray structure disclosed complex (1) crystallize in the Orthorhombic space group P2(1)2(1)2(1) with Z=4. The crystal structure contains heteronuclear units of [(SCN)Cd(L-1)Pb(NCS)](n), linked by a mu(1,1,)3 thiocyanate(SCN-) bridging. Here weak S center dot center dot center dot S chalcogen, Pb center dot center dot center dot S tetrel bonding with two C-H center dot center dot center dot pi(SCN) and one C-H center dot center dot center dot pi(arene) like interactions are vividly observed. The QTAIM/NCI diagram successfully explains the nature of these contacts. Hirshfeld surface (HS) and 2D fingerprint plots analysis has described the non-covalent supramolecular features. The H center dot center dot center dot H interactions dominate the solid-state crystal structure. The complex fluorescence behaviour is eventually quenched in the presence of explosive nitroaromatic compounds. Complex (1) retained high fluorescence sensitivity and selectivity only for organo-toxin trinitrophenol (TNP). The Stern-Volmer equation evaluated the enhancement of the fluorescence mechanism, the limit of detection (LOD), and the quenching constant (K SV), which for TNP is 6.92 x10(4) M-1. The turn-offfluorescence sensing mechanism is explained by (a) AIM/RDG surface interactions energy, (b) Charge-transfer complex, (b) Photo-induced electron transfer (PET) through the HOMO-LUMO approach, (c) Fluorescence resonance energy transfer (FRET), and (d) H-1 NMR titration. Notably, the active dynamic sensing is due to a decrease in fluorescence lifetime after the successive addition of TNP with the polymer. Finally, the title complex (1) is employed as a quenched fluorescence response sensor for detecting TNP in a dispersed aqueous medium. (c) 2022 Elsevier B.V. All rights reserved.