Dicondensed indolinobenzospiropyrans as precursors of thermo‐ and photochromic spiropyrans. Part II: assignment of ¹H and ¹³C NMR spectra

Abstract

The (1)H and (13)C NMR spectra of dicondensed indolinobenzospiropyrans as precursors of thermo- and photochromic spiropyrans, DC1-DC5, were completely assigned. Especially, the (1)H assignment and coupling characteristics of the diastereotopic protons at the carbon-3 position of the benzopyran rings were achieved by conducting (1)H-(1)H COSY and nOe experiments. The dihedral angles (theta(1), theta(2) and theta(3)) calculated from the experimental values of the vicinal coupling constants ((3)J) of DC5 are in good agreement with the observed values in the solid state. All of the carbons in the DC dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR) and DEPT135.

Isomerization of spirobenzopyrans bearing electron-donating and electron-withdrawing groups in acidic aqueous solutions

“…These assignments for compound 5b were coincident with the literatures. 22,23 3.2 UV-visible spectroscopy 3.2.1 Isomerization by acid-base changes. Fig.…”

Acceptor Influence on Thiolate Sensing by Hemicyanine Dyes

“…In 1:1 DMSO- d 6 –D 2 O (Figure S4C), the adduct displayed a pair of doublets for the trans double-bond at 5.98 and 6.59 ( J = 16.1), suggesting formation of a C 2 -adduct. Its C 2 resonance occurred at 101.2 ppm, which is similar in chemical shift to the sp 3 -spirocarbon of the closed-form of indolino-benzospiropyran dyes that contain an attached phenolic oxygen atom and resonate at ∼104 ppm in CDCl 3 . The 1 H– 13 C HMBC spectrum of the reaction mixture revealed through-bond correlations between C 2 (101.2) with H b (6.59), H a (5.98); N 1 -Me (2.55); and the two C-methyl groups of the Ind moiety (Figure S5).…”

Deuterated dicondensed indolinobenzospiropyran formed from the reaction of Fischer base-d2 and salicylaldehyde: Mechanism involving a carbinol intermediate

“…The structure of the dicondensed product has been reported in our previous paper [16], along with 1 H and 13 C NMR spectroscopic data, but the formation mechanism has now been reconsidered. Therefore, the deuterium content (x-value) of the deuterated DC (DC-d x ) molecules from reaction of excess Fischer base-d 2 with salicylaldehydes was needed to be evaluated, as this may enable the differentiation of two previously suggested mechanistic pathways (see text).…”

“…For the evaluation of the extent (x-value) of the deuterated DC (DC-d x ) formed, ratios of (Ha þ Ha 0 )/Hc were obtained from 1 H NMR data of the deuterated DC. With the knowledge of the structure of the dicondensed product and 1 H and 13 C NMR spectroscopic data previously reported [16], the experimental x-values were able to be obtained and compared with calculated values. Since 35% of the 2 0 -methylene of FB molecule was deuterated, the residual Hc is 65% in 1 H NMR data.…”

“…Although dicondensed products have provoked considerable discussion [15][16][17][18], including their X-ray crystal structures and spectroscopic characterization, the mechanism of their formation has not been previously rationalized. Two reasonable variations of a mechanistic pathway were suggested earlier for the formation of DC molecules from reaction of a Fischer base and salicylaldehydes [1,2].…”