希夫碱与介孔分子筛纳米超分子材料的发光

Luminescence of Nanosized Supramolecular Materials Composed of Host Mesoporous Molecular Sieves and Guest Schiff Bases

合成了希夫碱N,N′2亚水杨基1,4苯二胺(L1)、4[2羟基1萘甲醛基]苯甲酸(L2)和4[2羟基1苯甲醛基]苯甲酸(L3)。使用1HNMR、IR、UV和元素分析手段对希夫碱的结构进行表征。荧光光谱表明固体粉末希夫碱的L1、L2和L3具有较强的光致发光性能,多个精细特征激发峰,其荧光强度大小顺序为L1>L2>L3。荧光时间分辨实验表明,L1、L2和L3的荧光寿命分别为199,199,214ns。L1、L2和L3在乙醇溶液中荧光强度的顺序则为L3>L2>L1。希夫碱L3、L2和L1的乙醇溶液的荧光量子产率大小分别为0.60,0.56和0.0086。希夫碱L1、L2或L3与(CH3)3Si MCM41超分子材料的发光强度比与MCM41组装的强,说明疏水的分子筛环境有利于客体的发光。客体分子L1、L2和L3的激发光谱存在多个精细的激发峰,最大激发波长皆为468nm。希夫碱L1、L2或L3与分子筛形成的超分子材料的发射峰一般朝短波方向移动;L1、L2与(CH3)3Si MCM41及L2、L3与MCM41组装形成超分子体系后,最大激发峰分别红移到529,507,507,505nm;超分子MCM41L1和(CH3)3Si MCM41L3的最大激发峰波长则保持不变。L1、L2和L3分别与(CH3)3Si MCM41形成的超分子体系的荧光寿命则有较大的变化;而L1、L2和L3分别与MCM41形成超分子体系的荧光寿命几乎没有发生变化。荧光时间分辨实验说明主体对希夫碱客体具有很强的选择性。

The Schiff bases of N, N′-bis(salicylidene)-1,4-diaminobenzene (L_1), 4-[2-(hydroxy-1-naphthalen-1-ylmethylene)-amnio]-benzoic acid (L_2) and 4-(benzylidene-amino)-benzoic acid (L_3) are synthesized and characterized by ~1H NMR, IR, UV, and elemental analysis. The results of fluorescent spectra indicate that the Schiff bases of L_1, L_2, and L_3 possess strong luminescent properties. The excitation spectra of the Schiff bases have many fine characteristic excitation peaks and the maximal excitation wavelengths are 468 nm. The fluorescent lifetime experiments indicate that the lifetimes of the Schiff bases of L_1, L_2, and L_3 are 199, 199, and 214 ns, respectively. The sequence of the fluorescent intensity of the fine powder Schiff bases is listed as L_1>L_2>L_3, but the sequence of the ethanol solutions of Schiff bases is just reverse. The quantum yields of the ethanol solutions of L_3, L_2 and L_1 are 0.60, 0.56 and 0.008 6. The luminescent intensities of nanosized supramolecular materials that the guests of Schiff bases are encapsulated in the non-poplar channels of (CH_3)_3Si-MCM-41 are stronger than that of the composites encapsulated in the polar channels of MCM-41. The results show that the lipophilic channels of host are more favourable to fluorescence of the guest Schiff base molecule than the hydrophilic channels. Comparing with the excitation and emission peaks of the guest Schiff bases, the emission peaks of nanosized supramolecular materials shift generally blue. The excitation wavelengths of (CH_3)_3Si-MCM-41-L_1, (CH_3)_3Si-MCM-41-L_2, MCM-41-L_2 and MCM-41-L_3 are 529, 507, 507 and 505 nm (red shift), respectively. The excitation wavelengths of MCM-41-L_1 and (CH_3)_3Si-MCM-41-L_3 are the same as that of the guest Schiff bases. The lifetimes of (CH_3)_3Si-MCM supramolecular systems with L_1, L_2 and L_3 as guest has obvious change, but that of MCM-41 supramolecular systems with L_1, L_2 and L_3 as the guest keep almost unchanged, comparing with the guests of the schiff bases molecules. The experimental (results) of fluorescent lifetime show that the selectivity between the host and the guest exists obviously.