发光共价有机骨架LCOF-NDT1荧光识别甲醛的理论研究

基于密度泛函理论(DFT)和含时密度泛函理论(TD-DFT),探究了发光共价有机骨架LCOF-NDT1与甲醛之间的分叉氢键作用.发现LCOF-NDT1与甲醛氢键作用后发光机理发生改变.氢键复合物的电子激发能减小,激发态下的氢键键长变短,氢键质子供体的~1H-NMR移向高场,氢键质子供体和受体的振动频率发生红移,均表明电子激发态下的氢键增强.氢键复合物的荧光速率系数减小,内转换速率系数增大,阐明电子激发态下氢键的增强有利于非辐射跃迁,不利于辐射跃迁,从而导致LCOF-NDT1荧光减弱或猝灭.计算结果表明LCOF-NDT1在荧光识别甲醛方面有潜在的应用前景.

Theoretical investigation on fluorescence recognition of formaldehyde by LCOF-NDT1

Based on density functional theory(DFT)and time-dependent density functional theory(TD-DFT),furcated hydrogen bonds between LCOF-NDT1 and formaldehyde have been investigated.The calculation results indicate that the luminescence mechanism of LCOF-NDT1 changes after hydrogen bonding with formaldehyde.The electronic spectrum of hydrogen bond complex is red-shifted,hydrogen bond lengths in the excited state are shortened,~1H NMR shifts to the high field,vibrational frequencies of hydrogen bond donor and acceptor groups are red-shifted,all of them indicate that excited state hydrogen bonding behavior is enhanced.Furthermore,fluorescence emission rate constant of the hydrogen bonded complex decreases and internal conversion rate constant increases.It illustrates that electronic excited state hydrogen bond strengthening is conducive to non-radiative transitions and not beneficial to radiation transitions which lead to fluorescence emission weakening or quenching of LCOF-NDT1.These calculations indicate that LCOF-NDT1 has potential applications in fluorescence recognition of formaldehyde.