巨型给-受体分子开关化合物的合成及性质研究

A Gaint Donor-Acceptor Molecular Switch Compound:Synthesis and Properties

以构象可变的间苯二酚杯[4]芳烃孔穴化合物(Cavitand)为分子开关母体,合成了一种新颖的给-受体(D-A)型分子开关化合物(化合物1),该分子是目前已知分子量最大的D-A型间苯二酚杯[4]芳烃Cavitand(分子量为3064.9966).其中,以卟啉为给体,富勒烯为受体.在pH诱导下,化合物1可发生构象变化,即由原来的关闭状(vase)转为打开状(kite);而在降低温度和引入Zn^(2+)的条件下,不能促使化合物1发生构象变化.p H诱导构象发生变化的原因,是酸的加入会导致喹喔啉手臂上的N原子发生质子化,从而使得形成的静电排斥作用促使手臂之间相互远离.此外,对化合物1的光物理性质研究表明,存在卟啉向富勒烯的单线态能量转移,其单线态能量转移速率常数为1.1×10^(7)s^(-1),单线态能量转移效率为9.63%.

A novel donor-acceptor(D-A)molecular switch compound(compound 1)in which porphyrin is the donor and fullerene is the acceptor was synthesized using a conformationally variable resorcin[4]arene cavitand as the molecular switch parent.As far as we know,this molecule is the largest D-A resorcin[4]arene cavitand(molecular weight:3064.9966).In order to synthesize this D-A molecular switch,firstly,compounds 4 and 9 were synthesized by Sonogashira coupling and Suzuki coupling,respectively.Then,both compounds 4 and 9 react with compound 5 to obtain arm compounds 6 and 10.Considering the low yield in the process of synthesizing porphyrins,compound 6 was first reacted with resorcin[4]arene 11 to obtain compound 12.Undoubtedly,a by-product with two compound 6 arms simultaneously will be produced.So,compound 12 can be obtained in a higher yield by adding compound 6 in batches.Then compound 13 can be obtained by the Prato reaction,and finally,compound 1 can be obtained by reacting with porphyrin arm 10.The structure of 1 was thoroughly confirmed by ^(1)H NMR spectroscopy(nuclear magnetic resonance spectroscopy),^(13)C NMR spectroscopy,2D(two-dimensional)NMR spectroscopy and HRMS(high-resolution mass spectrometry).Under pH induction,compound 1 can undergo a conformational change from the original contracted state(vase)to the expanded state(kite).However,the conformational change of 1 cannot be induced under the conditions of lowering the temperature and introducing Zn^(2+).The reason for the pH-induced conformational change may be that the addition of acid causes the protonation of the N atom on the quinoxaline arm,which makes the formed electrostatic repulsion push the arms away from each other.In addition,the photophysical properties of 1 were also studied.The photophysical processes were investigated with steady-state UV-visible absorption and transient fluorescence spectroscopies.Compound 1 shows efficient intramolecular singlet-singlet energy transfer from the porphyrin moiety to the fullerene moiety.The rate constants and efficiency of the singlet-singlet energy transfer are calculated at 1.1×10^(7) s^(-1)and 9.63%,respectively.