2021 Ligand Effects on Electronic, Magnetic, and Catalytic Properties
Total Page：16
File Type：pdf, Size：1020Kb
2021 Ligand Effects on Electronic, Magnetic, and Catalytic Properties of Clusters and Cluster Assemblies Dinesh Bista Virginia Commonwealth University © Copyright by Dinesh Bista, 2021 All Rights Reserved Ligand Effects on Electronic, Magnetic, and Catalytic Properties of Clusters and Cluster Assemblies A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Nanoscience & Nanotechnology at Virginia Commonwealth University by Dinesh Bista Director: Shiv N. Khanna, Ph.D. Chairman and Commonwealth Professor, Department of Physics Virginia Commonwealth University Richmond, Virginia July 2021 Dedicated to my late Sister Devi Bista ii ACKNOWLEDGMENTS I want to express my genuine thankfulness and warm admiration to my graduate supervisor Professor Dr. Shiv N. Khanna, for his expertise and encouragement during my graduate study. His everlasting ideas in research methodology and his energy significantly encouraged me to reform my thinking and working methods. His guidance and continuous support are not only limited to educational work, but they have inspired me in other essential aspects of my life. I want to thank Dr. Vikash Chauhan, Shailendra Chand, Dr. Suyesh Koyu, and Dr. Meghnath Neupane for their valuable reviews, teachings, and inspiration during my graduate studies. I am obliged to my parents for their unwavering love and encouragement throughout my life. I want to dedicate this work to my late sister (Devi Bista), who always wanted to see my progress in every step of my life. I want to thank my Mother Shakuntala Bist and Father Khem Bahadur Bist. I am equally indebted to my Wife, Alisha Bhandari, for her unwavering support and inspiration throughout my Ph.D. journey. Similarly, I would like to thank my Sisters Kamala Bist and Bimala Bhandari, Brothers Krishna Bist, Dilip Gautam, Brother-in-laws Laxman Bhandari, and Hari Bhandari, uncles, Ram Kumar Basnet, Hari Basnet, Sher Bahadur Basnet, and Surya Bahadur Basnet, and all other family members for all the help and support during my graduate studies. Besides, I want to thank my year and half old Son Aiden for filling my life with joy. I am obliged to take this opportunity to sincerely thank Prof Jason Reed, Prof Marilyn Bishop, Prof Arthur C Reber, and Dr. Turbasu Sengupta for guiding me on the right path during my graduate studies. I am also thankful to my teachers Indra Jaishy and Bishnu Rai, from high school I want to express my special thanks to my wonderful friends and cousin brothers Puranjan Ghimire, Madhav Ghimire, Hemanta Banjade, Lal Bahadur Kunwar, Gaurav Ojha, Bipin Acharya, Utsav Basnet, Rajin Thapa, Roshan Thapa, Pranav Pant, Aashish Dhungana, Aavash Chapagain, Diwakar Pudasaini, Kapil Marhatta, Arjun Subedi, Sudesh iii Baral, TaraDev Bhattarai, Gyanu Shah, Deependra Lama, Birendra Chand, Bikram Bam, Kamal Bam, Harendra Pandey, Sanjay Limbu, Jeevan Magar, Navin Bam, Anil Swar, Prad Poudel, and Avinash Poudel. They have always been with me during my difficult and cherished moments. Although my words may not suffice to express my gratefulness, I am thankful to all my teachers, family members, group members, and friends who have always helped and encouraged me throughout my Ph.D. journey. iv Contents List of Figures ...............................................................................................................................vii List of Tables ................................................................................................................................xv Abstract ........................................................................................................................................xvi Organization of Thesis…………………………………………………………………………xvii 1 Introduction to Clusters and Ligated Cluster Assemblies…........................................................1 Atomic Clusters……………………………………………………...................................2 Superatoms …………………………………………………………………...……..........5 Metal Clusters……………………………………….........................................................8 Cluster Assembled Materials…………............................................................................ 12 Ligands …………………..................................................................................................13 Motivations…………………………………………………………………..…..............14 2 Density Functional Theory and Computational Methods.......................................................... 25 Background ...................................................................................................................... 25 Kohn-Hohenberg Theorems……………………………………………………….......... 28 Kohn-Sham Methods.........................................................................................................28 Exchange Correlation Functional……………………………………………..................31 Computational Methods ....................................................................................................34 3 Transforming Redox Properties of clusters using phosphine Ligands.......................................38 4 Fused Superatomic Dimer ..........................................................................................................61 Superatomic Molecules with Internal Electric Fields for Light Harvesting .....................62 A Magnetic Superatomic Dimer with an Intense Internal Electric Dipole and Magnetic Moment......................................................................................................74 v Interfacial Magnetism in Fused Superatomic Cluster [Co6Se8(PEt3)5]2………...............90 5 A ligand-induced homojunction between Aluminum-based clusters.......................................110 6 Ligand Effects in Heterogeneous catalysis using Palladium clusters on supported Defected graphene, reduced graphene oxide, and graphene acid.................................................................135 Background……………………......................................................................................135 Results and Discussion………........................................................................................141 7 Summary and Future Directions...............................................................................................154 Appendix......................................................................................................................................159 vi List of Figures Figure 1.1. (a) Regime of solids with respect to lengthscale (b) Variation in Physical Properties of materials with number of atoms……………………………......................................................3 Figure 1.2. (a) Mass Abundance spectrum of Sodium “Na” clusters (b) Series of mass spectra showing the progression of the etching reaction of aluminum cluster anions with oxygen - - showing peaks at Al13 and Al23 ………………….........................................................................4 - - Figure 1.3. Energy levels in atoms and clusters. Electronic levels in a Cl atom and Al13 cluster...............................................................................................................................................5 Figure 1.4. A pictorial representation of the periodic table of atomic and superatomic orbitals....6 Figure 1.5. Cluster stabilizations explained through NFE, Wade-Mingos, and covalent bonding..7 - Figure 1.6. First superatoms: Al13 and Al13 ………………………………………………………8 Figure 1.7. Optimized ground state structure of Pd13 cluster…………………………...................9 Figure 1.8 The HOMO-LUMO gap of the M6Se8L6 clusters, with L=CO, and PH3, and M=Y-Pd, and La, Hf-Pt. For CO ligated clusters, charge states of +2, 0, and -2 were studied, while for PH3 ligated cluster charge states of +4, +2 and 0 are shown...................................................................10 Figure 1.9 Library of SACs self-assembled using complementary charge transfer between superatomic building blocks..........................................................................................................13 Figure 1.10 Metal chalcogenide and gold clusters stabilized in different ligand environments. ........................................................................................................................................................14 Figure 1.11 The Selected SACs and their atomic structural analogues. Supporting ligands in all of the SACs have been removed for clarity. (a)[Co6Te8(PEt3)6][Fe8O4pz12Cl4] and CsCl; (b) vii [Ni9Te6(PEt3)8][C60] and NaCl; (c) [Co6Se8(PEt3)6][C60]2 and CdI2; (d) [Ni12Te12(PEt3)8]2[(Lu3N@C80)2] and Rb2O2.................................................................................16 Figure 1.12 (a) Successive replacement of PEt3 ligand by CO ligand (b) IP and EA with subsequent replacement of PEt3 ligands by CO ligands. (c) The plot of total charge with the subsequent exchange of PEt3 ligands by CO ligands.........................................................................................17 Figure 1.13 (a) IE drop on PEt3 ligation (b) Schematic of formation of ionic solid Ni9Te6(PEt3)8.C60...........................................................................................................................18 Figure 1.14 (a) ground state structures of Ni9Te6(CO)n (n=8-0) (b) modulation of magnetic moments with CO and PR3 ligands (c) A molecular orbital diagram of Ni9Te6(CO)8 and Ni9Te6(CO)7. HOMO corresponds to 0 eV......................................................................................19 − Figure 1.15 Negative ion