Molecular engineering of intensely near-infrared absorbing excited states in highly conjugated oligo(porphinato)zinc-(polypyridyl)metal(II) supermolecules
Molecular engineering of intensely near-infrared absorbing excited states in highly conjugated oligo(porphinato)zinc-(polypyridyl)metal(II) supermolecules
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DOI：
10.1021/ja0707512
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发表时间：
2007-08-08
影响因子：
15
通讯作者：
Therien, Michael J.
中科院分区：
文献类型：
--
作者：
Duncan, Timothy V.;Ishizuka, Tomoya;Therien, Michael J.
合成并表征了一种结合乙烯桥接双（三吡啶基）金属(II)-（卟啉）锌（II） （MPZn）和乙烯桥接（卟啉）锌（II） （PZnn）结构的新发色团MPZnn，以及一系列在附属三吡啶单元(Pyr（m)MPZn(n)）上带有吡咯烷基电子释放基团的衍生物。循环伏安研究，以及核磁共振、电子吸收、荧光和飞秒泵探瞬态吸收光谱，已经被用来研究这些不寻常的发色团的基态和激发态特性。所有这些物种都具有强烈吸收激发态，具有大的光谱带宽，穿透深近红外（NIR）能量状态。分子骨架的电子结构变化表明，激发态吸收最大值可以被广泛调制[lambda(max)(T-1 -> T-n)] (880 nm < lambda(max) < 1126 nm)，同时保持令人惊叹的T-1 -> T-n吸收流形光谱带宽（半最大值全宽度，fwhm，类似于2000-2500 cm(-1)）。此外，这些研究使超分子电子结构与激发态寿命（tau(es)）的大小相关，并证明该参数可以被调制超过4个数量级（类似于1 ns < tau(es) < 45 mu s）。三吡啶基吡啶基取代基可以破坏三吡啶基配体pi*能级的稳定性，降低双（三吡啶基）金属（II）中心的E-1/2 （M3+/2+）值：这些扰动决定了pzn衍生的(1)pi-pi*和双（三吡啶基）金属（II）电荷转移态的相对能量，并确定了MPZn和Pyr(m)MPZn(n)的t -1态波函数是否表现出在近红外强吸收的长寿命三重态的广泛电子离域和电荷分离（CS）特征。
A new series of chromophores, MPZnn, which combine ethyne-bridged bis(terpyridyl)metal(II)-(porphinato)zinc(II) (MPZn) and oligomeric, ethyne-bridged (porphinato)zinc(II) (PZnn) architectures, have been synthesized and characterized, along with a series of derivatives bearing pyrrolidinyl electron-releasing groups on the ancillary terpyridine units (Pyr(m)MPZn(n)). Cyclic voltammetric studies, as well as NMR, electronic absorption, fluorescence, and femtosecond pump-probe transient absorption spectroscopies, have been employed to study the ground- and excited-state properties of these unusual chromophores. All of these species possess intensely absorbing excited states having large spectral bandwidth that penetrate deep in the near-infrared (NIR) energy regime. Electronic structural variation of the molecular framework shows that the excited-state absorption maximum can be extensively modulated [lambda(max)(T-1 -> T-n)] (880 nm < lambda(max) < 1126 nm), while concomitantly maintaining impressively large T-1 -> T-n absorption manifold spectral bandwidth (full width at half-maximum, fwhm, similar to 2000-2500 cm(-1)). Furthermore, these studies enable correlation of supermolecular electronic structure with the magnitude of the excited-state lifetime (tau(es)) and demonstrate that this parameter can be modulated over 4 orders of magnitude (similar to 1 ns < tau(es) < 45 mu s). Terpyridyl pyrrolidinyl substituents can be utilized to destabilize terpyridyl ligand pi* energy levels and diminish the E-1/2 (M3+/2+) value of the bis(terpyridyl)metal(II) center: such perturbations determine the relative energies of the PZnn-derived (1)pi-pi* and bis(terpyridyl)metal(II) charge-transfer states and establish whether the T-1-state wave functions of MPZnn and Pyr(m)MPZn(n) species manifest the extensive electronic delocalization and charge-separated (CS) features characteristic of long-lived triplet states that absorb strongly in the NIR.