Periodic Reporting for period 1 - ReaDy-NMR (Relativistic and Dynamic effects in Computational NMR Spectroscopy of transition-metal complexes)
Okres sprawozdawczy: 2019-01-15 do 2021-01-14
Nuclear Magnetic Resonance (NMR) spectroscopy is among the most important means of characterization for transition-metal complexes. In this regard, the accurate prediction of NMR properties provides a useful, yet challenging, strategy to help in the interpretation of the spectra. The enormous challenge when modelling NMR spectra of heavy-nuclei arises from the extreme sensitivity to relativistic and solvent effects. Therefore, the calculation of NMR parameters in these systems is not an easy task and requires elaborate computational models. ReaDy-NMR project aimed to establish a computational protocol to determine NMR chemical shifts of transition-metal complexes by accurately taking into consideration relativistic effects and conformational dynamics. To successfully determine the chemical shifts, this protocol involved the use of all-electron two- (2c) and four-component (4c) relativistic quantum methods combined with ab-initio molecular dynamics (AIMD) simulations for the inclusion of the relativistic and solvent effects, respectively.
ReaDy-NMR selected diverse transition-metal complexes with significant potential applications in biomedicine, biotechnology, and industrial processes. Ready-NMR was focused on 1) series of new Au(III) catalysts, interpreting the NMR signals observed in the experimental spectra, 2) iridium polyhydride complexes, validating the hydride positions and assignments previously made, and 3) Pt(II) host-guest complexes, modelling the NMR spectra and contributing to the design of new anticancer Pt(II) host-guest macrocyclic systems. The research activities and goals of the project were diversified by including Sn(IV) halide complexes, interpreting the NMR signals observed in the experimental spectra. Accordingly, the proposed protocol included the validation of the structures, solvent, and relativistic effects on each of the selected complexes.
The main results achieved in ReaDy-NMR can be summarized as follows: The influence of relativistic and solvent effects on the 1H NMR chemical shifts calculations was explored on selected asymmetric Au(II) species in solution. The prediction of the static 1H NMR chemical shifts was determined using a relativistic 2c and fully 4c approaches and including an implicit solvent model. In addition, AIMD simulations were used to include conformational dynamics and calculate dynamic 1H NMR chemical shifts. Our approach confirms the observed NMR signature and the dynamic behavior of these species; the results of this study have been submitted for publication. In a separate study of catalytic iridium polyhydride complexes, a DFT protocol including relativistic, solvent, and dynamic effects at high level of theory was determined (Inorg. Chem. 2020, 59, 17509). This work provides a useful, yet challenging, strategy to help in the interpretation of 1H NMR hydride chemical shifts of complex metal polyhydrides. The 1H NMR chemical shifts of iridium polyhydride complexes were determined by combining first-principles calculations capable to accurately represent the interactions within the complex and the environment. Using this protocol, we were able to reliably model both the terminal and bridging hydride chemical shifts and to show that two NMR hydride signals were inversely assigned in the experiment.
A protocol for the modelling of NMR spectra in new Pt(II)-based host-guest systems was also proposed. NMR spectroscopy is a valuable tool for the characterization of these complexes as well as for the study of the host-guest complexation under physiological conditions. The theoretical analysis of NMR shifts was therefore essential to successfully determine their electronic and molecular structure. The manuscript including these results has been submitted for publication. In a separate study, the solution and solid-state 119Sn NMR chemical shifts of neutral hexacoordinate Sn(IV) halide complexes with 4,4’-Dimethyl-2,2’-bipyridine (DMB) were analyzed by combining experimental and theoretical methods (Z. Anorg. Allg. Chem. 2020, 646, 1274). The calculated 119Sn NMR chemical shifts were compared with the experimental signals and the effects of the structure and solvent on the NMR calculations were discussed. In addition, computational DFT methods were employed to gain more insight into the nature of the bonding in these complexes, including the prediction of the (DMB)SnX4(X=F, As) species.
ReaDy-NMR contributed with a book chapter devoted to the field of Computational NMR Spectroscopy (Chapter 2: Recent Advances in Computational NMR Spectrum Prediction, 2020, pp. 41-68, ISBN: 978-1-78801-461-8). This chapter serves as an overview of the field of computational simulation of NMR spectra as applied to chemistry and biology, drawing on recent advances as well as describing essential, established methods. Likewise, the results of ReaDy-NMR were presented in 5 national and international conferences; three invited/contributed talks and two posters.
The main results achieved in ReaDy-NMR can be summarized as follows: The influence of relativistic and solvent effects on the 1H NMR chemical shifts calculations was explored on selected asymmetric Au(II) species in solution. The prediction of the static 1H NMR chemical shifts was determined using a relativistic 2c and fully 4c approaches and including an implicit solvent model. In addition, AIMD simulations were used to include conformational dynamics and calculate dynamic 1H NMR chemical shifts. Our approach confirms the observed NMR signature and the dynamic behavior of these species; the results of this study have been submitted for publication. In a separate study of catalytic iridium polyhydride complexes, a DFT protocol including relativistic, solvent, and dynamic effects at high level of theory was determined (Inorg. Chem. 2020, 59, 17509). This work provides a useful, yet challenging, strategy to help in the interpretation of 1H NMR hydride chemical shifts of complex metal polyhydrides. The 1H NMR chemical shifts of iridium polyhydride complexes were determined by combining first-principles calculations capable to accurately represent the interactions within the complex and the environment. Using this protocol, we were able to reliably model both the terminal and bridging hydride chemical shifts and to show that two NMR hydride signals were inversely assigned in the experiment.
A protocol for the modelling of NMR spectra in new Pt(II)-based host-guest systems was also proposed. NMR spectroscopy is a valuable tool for the characterization of these complexes as well as for the study of the host-guest complexation under physiological conditions. The theoretical analysis of NMR shifts was therefore essential to successfully determine their electronic and molecular structure. The manuscript including these results has been submitted for publication. In a separate study, the solution and solid-state 119Sn NMR chemical shifts of neutral hexacoordinate Sn(IV) halide complexes with 4,4’-Dimethyl-2,2’-bipyridine (DMB) were analyzed by combining experimental and theoretical methods (Z. Anorg. Allg. Chem. 2020, 646, 1274). The calculated 119Sn NMR chemical shifts were compared with the experimental signals and the effects of the structure and solvent on the NMR calculations were discussed. In addition, computational DFT methods were employed to gain more insight into the nature of the bonding in these complexes, including the prediction of the (DMB)SnX4(X=F, As) species.
ReaDy-NMR contributed with a book chapter devoted to the field of Computational NMR Spectroscopy (Chapter 2: Recent Advances in Computational NMR Spectrum Prediction, 2020, pp. 41-68, ISBN: 978-1-78801-461-8). This chapter serves as an overview of the field of computational simulation of NMR spectra as applied to chemistry and biology, drawing on recent advances as well as describing essential, established methods. Likewise, the results of ReaDy-NMR were presented in 5 national and international conferences; three invited/contributed talks and two posters.
ReaDy-NMR project added significant computational advancements on the modelling of NMR spectra in transition-metal complexes, combining robust and non-conventional quantum-chemistry methodologies. Further development and application of the proposed protocol is highly desirable. The benefits of ReaDy-NMR are not limited in time and the results will continue to be used to predict, guide, and support NMR spectral assignments of other challenging systems, where sophisticated and reliable models are needed to determine the NMR properties.