Materials and methods. All the reagents were purchased from Sigma-Aldrich Pvt. Ltd. (India). Unless otherwise mentioned, materials were obtained from commercial suppliers and were used without further purification. Solvents were dried according to standard procedures. Elix Millipore water was used in all respective experiments. 1H and 13C NMR spectra were recorded on a Bruker 400 MHz instrument. For NMR spectra, DMSO-d6 and for NMR titration DMSO-d6 and D2O were used as solvent using TMS as an internal standard. Chemical shifts are expressed in δ ppm units and 1H–1H and 1H–13C coupling constants in Hz. The mass spectrum (HRMS) was carried out using a micromass Q-TOF MicroTM instrument by using methanol as a solvent. Fluorescence spectra were recorded on a PerkinElmer Model LS55 spectrophotometer. UV spectra were recorded on a SHIMADZU UV-3101PC spectrophotometer. The following abbreviations are used to describe spin multiplicities in 1H NMR spectra: s = singlet; d = doublet; t = triplet; m = multiplet. Single crystal X-ray data of CNP was measured using a dual-source Rigaku Super Nova diffractometer equipped with an Atlas detector and an Oxford Cryostream cooling system using mirror-monochromated Cu-Kα radiation (λ = 1.54184 Å). Data collection and reduction for both compounds were performed using the program CrysAlisPro and Gaussian face-index absorption correction method was applied. The structures were solved with Direct Methods (SHELXS)[30–32] and refined by full-matrix least-squares based on F2 using SHELXL-2015.[30–32] Non-hydrogen atoms were assigned anisotropic displacement parameters unless stated otherwise. The hydrogen atom bonded to nitrogen was located from Fourier difference maps and refined with an N−H distance restraint of approximately 0.96 Å. Otherhydrogen atoms were placed in idealised positions and included as riding. Isotropic displacement parameters for all H atoms were constrained to multiples of the equivalent displacement parameters of their parent atoms with Uiso(H) = 1.2 Ueq(parent atom). The single crystal X-ray data, experimental details as well as CCDC number are given in the Supporting Information.
Synthetic procedure of CNP: In a 100 ml round bottom flask, 2-hydroxy naphthaldehyde (1.0 g, 5.8 mmol) in 30 ml ethanol was vigorously stirred at ambient temperature for few minutes. Then, 3-amino-9-ethyl carbazole (1.46 g, 6.95 mmol) was dissolved in ethanol (10 mL) and added dropwise to the solution. The reaction mixture was refluxed for 24 hours at 83°C. After completion of the reaction (monitored by TLC), the solvent was evaporated completely under reduced vapor pressure, then extracted with chloroform and water. After drying it over anhydrous Na2SO4, the organic layer was evaporated completely to get the solid product. This product was purified by column chromatography with the eluent CHCl3:PET (5:1, v:v) to get the product CNP with 86% yield (Figure 7). 1H NMR (400 MHz, DMSO-d6): δ (ppm) = 16.37 (s, 1H), 9.84 (s, 1H), 8.57-8.59 (d, 2H, J=8Hz), 8.26-8.28 (d, 1H, J=8Hz), 7.90-7.92 (d, 1H, J= 8Hz), 7.77-7.82 (t, 2H, J=20Hz), 7.71-7.73 (d, 1H, J=8Hz), 7.62-7.64 (t, 1H, J=8Hz), 7.55-7.57 (t, 1H, J=8Hz), 7.47-7.51 (t, 1H, J=16Hz), 7.34-7.37 (t, 1H, J=12Hz), 7.23-7.26 (t, 1H, J=12Hz), 7.04-7.06 (d, 1H, J=8 HZ), 4.47-4.49 (q, 2H, J=8Hz), 1.31-1.34 (t, 3H, J=12Hz). 13C NMR (100 MHz, DMSO-d6): δ (ppm)= 169.46, 153.90, 140.30, 138.46, 135.94, 133.15, 129.04, 127.93, 126.67, 126.32, 123.28, 123.02, 122.26, 122.11, 120.92, 120.36, 119.55, 119.05, 112.08, 109.98, 109.52, 108.67, 37.19, 13.83. HRMS (TOF MS): (m/z, %): Calcd. for C25H20N2O: 364.1576. Found: m/z = 365.1283 (M+H+).