Department of Chemical Sciences, University of Naples Federico II, Napoli I-80126, Italy.
School of Life Science and Technology, Tokyo Institute of Technology, 4259-B55 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Inorg Chem. 2023 May 15;62(19):7515-7524. doi: 10.1021/acs.inorgchem.3c00852. Epub 2023 May 5.
Due to their unique coordination structure, dirhodium paddlewheel complexes are of interest in several research fields, like medicinal chemistry, catalysis, etc. Previously, these complexes were conjugated to proteins and peptides for developing artificial metalloenzymes as homogeneous catalysts. Fixation of dirhodium complexes into protein crystals is interesting to develop heterogeneous catalysts. Porous solvent channels present in protein crystals can benefit the activity by increasing the probability of substrate collisions at the catalytic Rh binding sites. Toward this goal, the present work describes the use of bovine pancreatic ribonuclease (RNase A) crystals with a pore size of 4 nm (321 space group) for fixing [Rh(OAc)] and developing a heterogeneous catalyst to perform reactions in an aqueous medium. The structure of the [Rh(OAc)]/RNase A adduct was investigated by X-ray crystallography: the metal complex structure remains unperturbed upon protein binding. Using a number of crystal structures, metal complex accumulation over time, within the RNase A crystals, and structures at variable temperatures were evaluated. We also report the large-scale preparation of microcrystals (∼10-20 μm) of the [Rh(OAc)]/RNase A adduct and cross-linking reaction with glutaraldehyde. The catalytic olefin cyclopropanation reaction and self-coupling of diazo compounds by these cross-linked [Rh(OAc)]/RNase A crystals were demonstrated. The results of this work reveal that these systems can be used as heterogeneous catalysts to promote reactions in aqueous solution. Overall, our findings demonstrate that the dirhodium paddlewheel complexes can be fixed in porous biomolecule crystals, like those of RNase A, to prepare biohybrid materials for catalytic applications.
由于其独特的配位结构，二钌桨轮配合物在许多研究领域都很有意义，如药物化学、催化等。以前，这些配合物被共轭到蛋白质和肽上，以开发作为均相催化剂的人工金属酶。将二钌配合物固定在蛋白质晶体中对于开发多相催化剂很有趣。蛋白质晶体中存在的多孔溶剂通道可以通过增加催化 Rh 结合位点处的底物碰撞概率来提高活性。为此，本工作描述了使用孔尺寸为 4nm（321 空间群）的牛胰腺核糖核酸酶（RNase A）晶体来固定[Rh(OAc)]并开发多相催化剂，以在水相介质中进行反应。通过 X 射线晶体学研究了[Rh(OAc)]/RNase A 加合物的结构：金属配合物结构在与蛋白质结合时保持不变。使用许多晶体结构，评估了金属配合物在 RNase A 晶体中随时间的积累、在不同温度下的结构以及在不同温度下的结构。我们还报告了[Rh(OAc)]/RNase A 加合物的微晶（∼10-20μm）的大规模制备以及与戊二醛的交联反应。通过这些交联的[Rh(OAc)]/RNase A 晶体进行了烯烃环丙烷化反应和重氮化合物的自偶联反应。该工作的结果表明，这些体系可作为多相催化剂用于促进水溶液中的反应。总的来说，我们的研究结果表明，二钌桨轮配合物可以固定在多孔生物分子晶体中，如 RNase A 晶体中，以制备用于催化应用的生物杂化材料。
