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CdSe Quantum Dots Functionalized with Chiral, Thiol-Free Carboxylic Acids: Unraveling Structural Requirements for Ligand-Induced Chirality
ACS Nano ( IF 15.8 ) Pub Date : 2017-10-02 00:00:00 , DOI: 10.1021/acsnano.7b03555 Krisztina Varga 1 , Shambhavi Tannir 2 , Benjamin E. Haynie 1 , Brian M. Leonard 2 , Sergei V. Dzyuba 3 , Jan Kubelka 2 , Milan Balaz 4
ACS Nano ( IF 15.8 ) Pub Date : 2017-10-02 00:00:00 , DOI: 10.1021/acsnano.7b03555 Krisztina Varga 1 , Shambhavi Tannir 2 , Benjamin E. Haynie 1 , Brian M. Leonard 2 , Sergei V. Dzyuba 3 , Jan Kubelka 2 , Milan Balaz 4
Affiliation
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Functionalization of colloidal quantum dots (QDs) with chiral cysteine derivatives by phase-transfer ligand exchange proved to be a simple yet powerful method for the synthesis of chiral, optically active QDs regardless of their size and chemical composition. Here, we present induction of chirality in CdSe by thiol-free chiral carboxylic acid capping ligands (l- and d-malic and tartaric acids). Our circular dichroism (CD) and infrared experimental data showed how the presence of a chiral carboxylic acid capping ligand on the surface of CdSe QDs was necessary but not sufficient for the induction of optical activity in QDs. A chiral bis-carboxylic acid capping ligand needed to have three oxygen-donor groups during the phase-transfer ligand exchange to successfully induce chirality in CdSe. Intrinsic chirality of CdSe nanocrystals was not observed as evidenced by transmission electron microscopy and reverse phase-transfer ligand exchange with achiral 1-dodecanethiol. Density functional theory geometry optimizations and CD spectra simulations suggest an explanation for these observations. The tridentate binding via three oxygen-donor groups had an energetic preference for one of the two possible binding orientations on the QD (111) surface, leading to the CD signal. By contrast, bidentate binding was nearly equienergetic, leading to cancellation of approximately oppositely signed corresponding CD signals. The resulting induced CD of CdSe functionalized with chiral carboxylic acid capping ligands was the result of hybridization of the (achiral) QD and (chiral) ligand electronic states controlled by the ligand’s absolute configuration and the ligand’s geometrical arrangement on the QD surface.
中文翻译：
CdSe量子点与手性，无硫醇的羧酸功能化：解开配体诱导的手性的结构要求。
通过相转移配体交换将具有手性半胱氨酸衍生物的胶体量子点（QD）功能化，是一种合成手性，旋光性QD的简单而有效的方法，无论其大小和化学组成如何。在这里，我们介绍通过无硫醇的手性羧酸封端配体（l和d诱导CdSe中的手性-苹果酸和酒石酸）。我们的圆二色性（CD）和红外实验数据表明，在CdSe量子点表面上存在手性羧酸封端配体是必需的，但不足以诱导量子点中的光学活性。手性双羧酸封端配体在相转移配体交换过程中需要具有三个氧供体基团才能成功诱导CdSe中的手性。通过透射电子显微镜和与非手性1-十二烷硫醇的反相转移配体交换，没有观察到CdSe纳米晶体的内在手性。密度泛函理论的几何优化和CD光谱模拟为这些观察结果提供了解释。三齿结合通过三个氧供体基团对QD（111）表面上两个可能的结合方向之一具有能量偏好，从而导致CD信号。相比之下，双齿结合几乎是等能的，导致消除了近似相反签名的相应CD信号。得到的被手性羧酸封端配体官能化的CdSe的诱导CD是（非手性）QD和（手性）配体电子状态杂交的结果，该电子状态受配体的绝对构型和配体在QD表面的几何排列控制。
更新日期：2017-10-02
中文翻译：
CdSe量子点与手性，无硫醇的羧酸功能化：解开配体诱导的手性的结构要求。
通过相转移配体交换将具有手性半胱氨酸衍生物的胶体量子点（QD）功能化，是一种合成手性，旋光性QD的简单而有效的方法，无论其大小和化学组成如何。在这里，我们介绍通过无硫醇的手性羧酸封端配体（l和d诱导CdSe中的手性-苹果酸和酒石酸）。我们的圆二色性（CD）和红外实验数据表明，在CdSe量子点表面上存在手性羧酸封端配体是必需的，但不足以诱导量子点中的光学活性。手性双羧酸封端配体在相转移配体交换过程中需要具有三个氧供体基团才能成功诱导CdSe中的手性。通过透射电子显微镜和与非手性1-十二烷硫醇的反相转移配体交换，没有观察到CdSe纳米晶体的内在手性。密度泛函理论的几何优化和CD光谱模拟为这些观察结果提供了解释。三齿结合通过三个氧供体基团对QD（111）表面上两个可能的结合方向之一具有能量偏好，从而导致CD信号。相比之下，双齿结合几乎是等能的，导致消除了近似相反签名的相应CD信号。得到的被手性羧酸封端配体官能化的CdSe的诱导CD是（非手性）QD和（手性）配体电子状态杂交的结果，该电子状态受配体的绝对构型和配体在QD表面的几何排列控制。
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