Electronic and spectral properties of ametal-organic super container molecule by single point DFT

ABSTRACT

Metal-organic super container (MOSC) molecules are ideal candidates for photocatalysis due to their construction with transition metal centres and tuneable cavity sizes that could house catalytic sites. The basic electronic structure for a model of extremely large size (more than 2000 ions) is explored by single point calculation using unrestricted density functional theory, and Perdue–Burke–Ernzerhof functional in Vienna ab initio simulation package software. The information obtained through these calculations (such as density of states, absorbance spectra, and charge density) will allow for analysis of a MOSC's catalytic ability. Electronic characteristics of the nanostructures (MOSCs and their building blocks) in the ground and photoexcited electronic configurations are examined. We explore if the presence of transition metal ions with open shells in such close proximity to one another may result in high spin configurations and show any arrangement into ferromagnetic ordering. Spin-unrestricted computation was applied to evaluate how optical properties could be affected by d–d transitions. A scan of a spin-polarisation parameter allows one to resolve spin configuration and obtain a connection between theory and experiment. Analysis of Kohn–Sham orbitals of interest provides insight into charge transfer mechanisms, which were found to contribute to multiple low-energy charge transfer states to the electronic structure.

KEYWORDS:

• Spin-unrestricted DFT
• optical properties
• ligand-to-metal charge transfer
• metal-organic frameworks
• MOF
• MOSC

Acknowledgements

Computations supporting this project were performed on high-performance computing systems at the University of South Dakota, with the assistance of the Research Computing Manager, Doug Jennewein. Additionally, this research used resources of the National Energy Research Scientific Computing Center (NERSC), a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, allocation award 88777, ‘Computational Modeling of Photo-catalysis and Photo-induced Charge Transfer Dynamics on Surfaces’. Zenqiang Wang acknowledges the financial support of an NSF CAREER Award (CHE-1352279) and a South Dakota Board of Regents Competitive Research Grant Program award. Dmitri Kilin acknowledges support of NSF Awards CHE-1413617 and CHE-1460872.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/00268976.2015.1076899.

Additional information

Funding

Zenqiang Wang acknowledges the financial support of an NSF CAREER Award [CHE-1352279]; South Dakota Board of Regents Competitive Research Grant Program award. Dmitri Kilin acknowledges support of NSF Awards [CHE-1413617 and CHE-1460872].