Novel naphthalimide–aminobenzamide dyads as OFF/ON fluorescent supramolecular receptors in metal ion binding

Experimental and theoretical study of novel aminobenzamide–aminonaphthalimide fluorescent dyads with a FRET mechanism

In this work, both experimental and theoretical methods were used to study the photophysical and metal ion binding properties of a series of new aminobenzamide–aminonaphthalimide (2ABZ–ANAPIM) fluorescent dyads. The 2-aminobenzamide (2ABZ) and 6-aminonaphthalimide (ANAPIM) fluorophores were linked through alkyl chains (C₂ to C₆) to obtain four fluorescent dyads. These dyads present a highly efficient (0.61 to 0.98) Förster Resonant Energy Transfer (FRET) from the 2ABZ to the ANAPIM due to the 2ABZ emission and ANAPIM excitation band overlap and the configurational stacking of both aromatic systems which allows the energy transfer. These dyads interact with Cu²⁺ and Hg²⁺ metal ions in solution inhibiting the FRET mechanism by the cooperative coordination of both 2ABZ and ANAPIM moieties. Both experimental and theoretical results are consistent and describe clearly the photophysical and coordination properties of these new dyads.

The aminobenzamide–aminonaphthalimide fluorescent dyads allow the determination of Cu²⁺ and Hg²⁺ metal ion concentration from Förster Resonant Energy Transfer measurements.

Interaction of aromatic compounds and anions with naphthylimide-dansylamide fluorescent dyad: Experimental evidence of aryl C-H…π and aryl C-H…anion contacts and DFT calculations

In this work the interaction of halide anions and simple aromatic compounds with a bichromophoric fluorescent dyad derived from 1,8-naphthalimide (NAPIM) and 5-(dimethylamino)naphthalene-1-sulfonyl (DANS) was studied using electronic spectroscopy, ¹H, and ¹⁹F NMR spectroscopy and quantum chemistry modeling (b3lyp/def2-TZVP). The NAPIM-DANS dyad interacts with electron-rich guests with binding constants in the range of 6×10³ to 8×10³M^-1 in CHCl₃. The formed complexes are stabilized through aryl C-H … anion and aryl C-H … π interactions.

Design and synthesis of naphthalimide group-bearing thioglycosides as novel β-N-acetylhexosaminidases inhibitors

GH20 human β-N-acetylhexosaminidases (hsHex) and GH84 human O-GlcNAcase (hOGA) are involved in numerous pathological processes and emerged as promising targets for drug discovery. Based on the catalytic mechanism and structure of the catalytic domains of these β-N-acetylhexosaminidases, a series of novel naphthalimide moiety-bearing thioglycosides with different flexible linkers were designed, and their inhibitory potency against hsHexB and hOGA was evaluated. The strongest potency was found for compound 15j (K_i = 0.91 µM against hsHexB; K_i > 100 µM against hOGA) and compound 15b (K_i = 3.76 µM against hOGA; K_i = 30.42 µM against hsHexB), which also exhibited significant selectivity between these two enzymes. Besides, inhibitors 15j and 15b exhibited an inverse binding patterns in docking studies. The determined structure–activity relationship as well as the established binding models provide the direction for further structure optimizations and the development of specific β-N-acetylhexosaminidase inhibitors.

Experimental evidence of TICT state in 4-piperidinyl-1,8-naphthalimide – a kinetic and mechanistic study

The excited state processes in N-propyl-4-piperidinyl-1,8-naphthalimide have been studied by measuring its fluorescence spectra and decay curves in solvents of different polarity and viscosity and also in a frozen solvent glass.

Photoinduced Electron Transfer Switching Mechanism of a Naphthalimide Derivative with its Solvatochromic Behaviour: An Experimental and Theoretical Study with In Cell Investigations

The sole existence of a t-bone-shaped naphthalimide derivative [2-(2-aminoethyl)-1H-benzo[de]isoquinoline-1,3(2H)dione] (NAP), which gives rise to a photoinduced electron transfer (PET) mechanism, has been established using a combination of experimental and theoretical studies. In parallel an in vitro-in cell PET mechanism has also been shown. To understand the photophysics of NAP, solvent studies have been carried out in different solvents. In addition, theoretical calculations have been conducted to explain the spectroscopic properties through optimized structures. A "turn off" PET mechanism has also been observed in the presence of specific metal ions, namely, Cr³⁺ , Fe³⁺ and Hg²⁺ among a series of metal ions. Theoretical studies reveal that NAP-Cr³⁺ , NAP-Fe³⁺ and NAP-Hg²⁺ have their HOMO energy states lying in between a HOMO-LUMO energy state of the t-bone-type NAP molecule. On the contrary, the HOMO state of the other metal ion-NAP conjugate (NAP-Mⁿ⁺ ) does not lie in between the HOMO-LUMO energy gap of the t-bone-type NAP molecule. Coupled with in vitro studies, in cell investigations reveal an enhancement of fluorescence intensity of NAP upon cytosolic metal sensing. Furthermore, a very high cell viability of NAP treated cells as tested by MTT assay and a fast permeation of the said compound as revealed by flow cytometry suggest NAP to be a potential candidate in metal sensing and bioimaging applications.

Crystal structure of N,N'-bis[2-((benzyl){[5-(di-methyl-amino)naph-tha-len-1-yl]sulfonyl}amino)ethyl]naphthalene-1,8:4,5-tetracarboximide 1,2-di-chloro-benzene tris-olvate

The asymmetric unit of the title compound, C56H50N6O8S2·3C6H4Cl2, contains two half-mol-ecules of the parent, A and B, which both have crystallographic inversion symmetry, together with three 2,3-di-chloro-benzene mol-ecules of solvation. Mol-ecules A and B are conformationally similar, with dihedral angles between the central naphthalenedi-imide ring and the peripheral naphthalene and benzyl rings of 2.43 (7), 81.87 (7)° (A) and 3.95 (7), 84.88 (7)° (B), respectively. The conformations are stabilized by the presence of intra-molecular π-π inter-actions between the naphthalene ring and the six-membered di-imide ring of the central naphthalenedi-imide moiety, with ring centroid-to-centroid distances of 3.5795 (8) Å (A) and 3.5640 (8) Å (B). In the crystal, C-H⋯O hydrogen bonds link the mol-ecules into infinite supra-molecular chains along the c axis. These chains are inter-connected through C-H⋯π and offset π-π inter-actions, generating supra-molecular nanotubes which are filled by 1,2-di-chloro-benzene mol-ecules.