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首页> 外文期刊>Chemistry: A European journal >Change in the Site of Electron-Transfer Reduction of a Zinc-Quinoxalinoporphyrin/Gold-Quinoxalinoporphyrin Dyad by Binding of Scandium Ions and the Resulting Remarkable Elongation of the Charge-Shifted-State Lifetime
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Change in the Site of Electron-Transfer Reduction of a Zinc-Quinoxalinoporphyrin/Gold-Quinoxalinoporphyrin Dyad by Binding of Scandium Ions and the Resulting Remarkable Elongation of the Charge-Shifted-State Lifetime

机译：通过Scan离子的结合改变锌-喹喔啉卟啉/金-喹喔啉卟啉二元电子转移还原的位点，并导致电荷转移态寿命的显着延长

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摘要

The site of electron-transferreduction of AuPQ+ (PQ = 5,10,15,20-tetrakis(3,5-di-tert-butylpheny1)quino-xalino[2,3-b]porphyrin) and AuQPQ+(QPQ = 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)bisquinoxalino[2,3-b':12,-13-blporphyrin) is changed from theAu~1llcenter to the quinoxaline part ofthe PQ macrocycle in the presence ofSc3+ in benzonitrile because of strongbinding of Sc~3+to the two nitrogenatoms of the quinoxaline moiety.Strong binding of Sc~3+to the corre-sponding nitrogen atoms on the qui-noxaline unit of ZnPQ also occurs forthe neutral form. The effects of Sc3+on the photodynamics of an electrondonor–acceptor compound containinga linked Zn~11 and Au~111 porphyrin([ZnPQ–AuPQ]PF_6) have been exam-fined by femto- and nanosecond laserflash photolysis measurements. The ob-served transient absorption bands at630 and 670 nm after laser pulse irradi-ation in the absence of Sc~3+ in benzoni-trile are assigned to the charge-shifted(CS) state (ZnPQ+-AuPQ). The CSstate decays through back electrontransfer (BET) to the ground staterather than to the triplet excited state.The BET rate was determined from thedisappearance of the absorption banddue to the CS state. The decay of theCS state obeys first-order kinetics. TheCS lifetime was determined to be 250 ps in benzonitrile. Addition of Sc3+to a solution of ZnPQ–AuPQ+ in ben-zonitrile caused a drastic lengtheningof the CS lifetime that was determinedto be 430 ns, a value 1700 times longerthan the 250 ps lifetime measured inthe absence of Sc~3+. Such remarkableprolongation of the CS lifetime in thepresence of Sc~3+results from a changein the site of electron transfer from theAu~111 center to the quinoxaline part ofthe PQ macrocycle when Sc~3+binds tothe quinoxaline moiety, which deceler-ate BET due to a large reorganizationenergy of electron transfer. The changein the site of electron transfer was con-firmed by ESR measurements, redoxpotentials, and UV/Vis spectra of thesingly reduced products.
机译：AuPQ +（PQ = 5,10,15,20-四（3,5-二叔丁基苯基1）喹喔啉[2,3-b]卟啉）和AuQPQ +（QPQ = 5在存在的情况下，将10,15,20-四（3,5-二叔丁基苯基）双喹喔啉[2,3-b'：12，-13-blphyphyrin）从Au〜1ll中心变为PQ大环的喹喔啉部分由于Sc〜3 +与喹喔啉部分的两个氮原子之间的牢固结合，导致苯甲腈中的Sc3 +发生了中性形式。通过飞秒和纳秒级激光闪光光解测量可以确定Sc3 +对包含连接的Zn〜11和Au〜111卟啉（[ZnPQ–AuPQ] PF_6）的电子给体-受体化合物的光动力学的影响。在苯甲腈中不存在Sc〜3 +的情况下，激光脉冲照射后在630和670 nm处观察到的瞬态吸收带被指定为电荷转移（CS）状态（ZnPQ + -AuPQ）。 CS态通过反电子传递（BET）衰减到基态而不是三重激发态。BET速率是由CS态吸收带的消失决定的。 CS状态的衰减服从一阶动力学。在苯甲腈中，CS寿命确定为250 ps。在苯甲腈中的ZnPQ–AuPQ +溶液中添加Sc3 +导致CS寿命急剧延长，确定为430 ns，该值比没有Sc〜3 +时测量的250 ps寿命长1700倍。 Sc〜3 +存在下CS寿命的如此显着延长是由于当Sc〜3 +结合到喹喔啉部分时，电子从Au〜111中心转移到PQ大环的喹喔啉部分的位置改变，从而使BET减速电子转移的重组能量很大。电子转移位置的变化由ESR测量，氧化还原电势和单个还原产物的UV / Vis光谱确定。

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