Unniram Parambil Ajmal Roshan, Pokratath Rohan, Parammal Muhammed Jibin, Dhaene Evert, Van den Eynden Dietger, Balog Sandor, Prescimone Alessandro, Infante Ivan, Shahgaldian Patrick, De Roo Jonathan
Institute of Chemistry and Bioanalytics, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland 4132 Muttenz Switzerland.
Department of Chemistry, University of Basel Mattenstrasse 22 4058 Basel Switzerland
Chem Sci. 2024 Oct 7;15(42):17380-96. doi: 10.1039/d4sc03859b.
The effectiveness of nanocrystals in many applications depends on their surface chemistry. Here, we leverage the atomically precise nature of zirconium and hafnium oxo clusters to gain fundamental insight into the thermodynamics of ligand binding. Through a combination of theoretical calculations and experimental spectroscopic techniques, we determine the interaction between the MO (M = Zr, Hf) cluster surface and various ligands: carboxylates, phosphonates, dialkylphosphinates, and monosubstituted phosphinates. We refute the common assumption that the adsorption energy of an adsorbate remains unaffected by the surrounding adsorbates. For example, dialkylphosphinic acids are too sterically hindered to yield complete ligand exchange, even though a single dialkylphosphinate has a high binding affinity. Monoalkyl or monoaryl phosphinic acids do replace carboxylates quantitatively and we obtained the crystal structure of MOH(OP(H)Ph) (M = Zr, Hf), giving insight into the binding mode of monosubstituted phosphinates. Phosphonic acids cause a partial structural reorganization of the metal oxo cluster into amorphous metal phosphonate as indicated by pair distribution function analysis. These results rationalize the absence of phosphonate-capped MO clusters and the challenge in preparing Zr phosphonate metal-organic frameworks. We thus further reinforce the notion that monoalkylphosphinates are carboxylate mimics with superior binding affinity.
纳米晶体在许多应用中的有效性取决于其表面化学性质。在此，我们利用锆和铪氧簇的原子精确性质，以深入了解配体结合的热力学原理。通过理论计算和实验光谱技术相结合的方法，我们确定了MO（M = Zr，Hf）簇表面与各种配体之间的相互作用：羧酸盐、膦酸盐、二烷基次膦酸盐和单取代次膦酸盐。我们反驳了一个普遍的假设，即吸附质的吸附能不受周围吸附质的影响。例如，二烷基次膦酸在空间位阻上太大，以至于无法实现完全的配体交换，尽管单个二烷基次膦酸盐具有很高的结合亲和力。单烷基或单芳基次膦酸确实能定量取代羧酸盐，并且我们获得了MOH(OP(H)Ph)（M = Zr，Hf）的晶体结构，从而深入了解了单取代次膦酸盐的结合模式。如对分布函数分析所示，膦酸会使金属氧簇发生部分结构重排，形成无定形金属膦酸盐。这些结果解释了膦酸盐封端的MO簇不存在的原因以及制备锆膦酸盐金属有机框架的挑战。因此，我们进一步强化了单烷基次膦酸盐是具有优异结合亲和力的羧酸盐模拟物这一观点。
