Salen-type Schiff bases are a kind of important compounds and are widely used. In order to explore the effect of alkyl groups and substituents attached to aromatic ring on the chemical shifts, 63 title compounds were synthesized.Their 1 H NMR and 13 C NMR spectra were obtained; and the effects of the alkyl chain length and substituents on the chemical shifts (δ H (CH N), δ C (CH N), δ H (OH), and δ C (C OH)) were studied. The results show that (1) the alkyl polarizability effect index (PEI) has an important influence on the chemical shifts of the above four atoms, with the increase of PEI, the values of δ H (CH N) and δc(CH N) decrease, and the values of δ H (OH) and δ C (C OH) increase. (2) The influence of substituent X attached to aromatic ring on the chemical shift is related to its position by taking OH or CH N as reference. As for the effect of substituent on the chemical shifts, the effect of Hammett constant σ(X) OH and excited-state substituent parameter σ ex CC X ð Þ OH with OH as reference are different from that ofσ(X) CH N and σ ex CC X ð Þ CH N with CH N as reference, and there is a "homoring competition effect" of the substituent.(3) The effect of the cross-interaction between X and OH on the chemical shift is also significantly different due to the different position of X. Quantitative correlation equations against chemical shifts were built for the four atoms, and the stability and prediction ability of the obtained equations were confirmed by leave-one-out cross validation.
To explore the effect of substituent attached to aromatic ring and the length of diamine chain in salen-type Schiff base molecules on the fluorescence emission spectra (FL em ), the FL em of 63 diamine-salicylaldehyde condensates in an ethanol solution were obtained. The influence of substituent electronic effects and chain lengths on the wavenumber (ν em ) of fluorescence emission wavelengths (λ em ) was subsequently studied. The results show that the length of the diamine chain in the target compound has an effect on the ν em , which can be quantified by the alkyl polarizability effect index (PEI), where compounds with alkyl of higher PEI have lower ν em . Second, the λ em of salen-type Schiff bases can be quantified by an equation of the seven parameters, PEI, σ(X) ─OH , σ(X) ─CH═N , σ ex CC X ð Þ ─OH , σ ex CC X ð Þ ─CH═N , Δσ 2 p and Δσ 2 m , form where the stability and predictive ability of the obtained equation was confirmed by leave-one-out cross validation. Lastly, it was observed that the influence on the λ em of substituent X attached to the aromatic ring is related to its position relative to OH or CH═N groups as reference, whose Hammett constants (σ(X) ─OH , σ(X) ─CH═N ) and the excited-state substituent constants (σ ex CC X ð Þ ─OH , σ ex CC X ð Þ ─CH═N ) of the substituents X with varying locating methods have different effects on the λ em ;and that there is a "homoring competition effect" of substituent.
C17H14Cl2CuN2O2, monoclinic, C2/c (no. 15), a = 22.743(4) Å, b = 8.0434(15) Å, c = 8.9388(17) Å, V = 1630.8(5) Å3, Z = 4, R
gt
(F) = 0.0376, wR
ref(F
2) = 0.0997, T = 296(2) K.
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