2
S. Yosefdad et al. / Journal of Molecular Structure 1200 (2020) 127105
Scheme 1.
White powder; yield: 0.43 g (82%); m.p. 245e247 ꢀC. 1H NMR
2. Experimental
(300 MHz, DMSO): 4.10 (2H, d, CH2), 7.71 (2H, m, ArH), 7.80 (2H, m,
ArH). 13C NMR (75.4 MHz, DMSO): 38.8, 123.3, 131.9, 134.0, 168.3. IR
(KBr) (ymax/cmꢁ1): 3274, 2062, 1631, 1200, 650. Anal. Calcd for
2.1. General
C
18H12N2O4 (320.30): C, 67.50; H, 3.78; N, 8.75. Found: C, 67.8; H,
The 1,n-diamine (GC grade: > 99%), phthalic anhydride (ACS
reagent grade: > 99%), pentane-2,4-dione (GC grade: > 99%), acetic
anhydride, triethylamine, ethanol (GC grade: > 99.5%), diethyl
ether, hexane were obtained from Merck and Aldrich and were
used without further purification. NMR spectra were recorded with
a Bruker DRX-300 Avance instrument (300 MHz for 1H and
75.4 MHz for 13C) with DMSO as solvent. Chemical shifts are given
3.5, N, 8.6.
in ppm (d) relative to internal TMS and coupling constant (J) are
reported in hertz (Hz). Melting points were measured with an
electrotherma1 9100 apparatus. Mass spectra were recorded with
an Agilent 5975C VL MSD with Triple-Axis Detector operating at an
ionization potential of 70 eV. The samples were introduced directly
to the ionization chamber. The ion source, and quadrupole tem-
peratures were set to 230 ꢀC, 150 ꢀC, respectively. The probe tem-
perature is variable depending on the melting point of samples. IR
spectra were measured with a Bruker Tensor 27 spectrometer
(Fig. S1 in Supplementary Materials). Elemental analyses for C, H
and N were performed using a PerkinElmer 2004 series [II] CHN
elemental analyzer.
(4) : 1.2.1. 2,2-(propane-1,3-diyl)bis(isoindoline-1,3-dione)
White powder; yield: 0.36 g (70%); m.p. 204e206 ꢀC. 1H NMR
3
(300 MHz, DMSO): 2.10 (2H, p, JHH ¼ 7.4 Hz, CH2), 3.78 (2H, t,
3JHH ¼ 7.4 Hz, CH2), 7.71 (2H, m, ArH), 7.80 (2H, m, ArH). 13C NMR
(75.4 MHz, DMSO): 27.6, 35.7, 123.3, 132.1, 134.0, 168.2. IR (KBr)
(
C
ymax/cmꢁ1): 2946, 1710, 1390, 1173, 1019, 720. Anal. Calcd for
19H14N2O4 (334.33): C, 68.26; H, 4.22; N, 8.38. Found: C, 68.6; H,
4.4, N, 8.2.
2.2. General procedure for the synthesis of 3
2.3. Computational details
To a solution of phthalic anhydride (1 mmol) and pentane-2,4-
dione or diethyl malonate (1 mmol) in acetic anhydride (0.56 ml)
at 25 ꢀC, triethylamine (2 mmol) was added dropwise and the
mixture stirred for 30 min. The reaction was quenched by the
addition of aqueous hydrochloric acid (2.3 ml of 1 M solution). The
resulting solid was collected by filtration, and washed with diethyl
ether (1.5 ml) and then with hexane (1.5 ml) to give 1 as colorless
crystals (Scheme 1). A mixture of diethyl-2-(3-oxo-2-isoindoline-1-
ylidene)malonate 1 (0.30 g, 1 mmol), 2-(nitromethylene)imidazo-
line 2 (1 mmol) and EtOH (5 ml) in a 50 mL flask was heated at
reflux for 3 h. After completion of the reaction [monitored by TLC
(Thin-Layer Chromatography), ethyl acetate/n-hexane, 1:1], the
reaction mixture was cooled to room temperature and the formed
solid filtered. The solid was washed with ethanol or recrystallized
from ethanol to give pure product 3 in high yield.
Structures of the neutral and cationic molecules as well as the
hydrated species were fully optimized by density functional theory
employing B3LYP functional. The basis set 6-31 þ G(d) including
diffuse and polarization functions were used for the calculations.
Also, the larger basis set 6e31þþG(d,p) was used for computing
thermodynamic data of the hydration reactions. The frequency
calculations were performed at the smae level to calculate the
thermodynamic quantities such as enthalpy (
DH) and Gibbs free
energy ( G) values of hydration. Both the vertical (VIE) and adia-
D
batic ionization energies (AIE) for the compounds 3 and 4 were
calculated at the same level of theory. In the case of VIE, the
structure of the neutral compound (M) was optimized and the
same geometry was used for its corresponding cation (Mþ). For the
AIE, the structures of both M and Mþ were optimized. The calcu-
lations in solvent (chloroform) were performed by Tomasi’s Polar-
ized Continuum Model (PCM) [27] at the same level of theory. All
calculations were carried out using Gaussian 09 software [28].
3. Result and discussion
3.1. Effect of structure on the fragmentation of 3 and 4
Fig. 1 shows the structures of the compounds 3 and 4, optimized
in gas phases. Two isomers, a and b, for each compounds were
considered. The isomers 3b and 4b are more stable in gas phase,
while the stability of the isomers 3a and 4a increases in CHCl3
(3) : 1.2.2. 2,2-(ethane-1,2-diyl)bis(isoindoline-1,3-dione)