title: Can Cyclen Bind Alkali Metal Azides? A DFT Study as a Precursor to Synthesis.
abstract: Can cyclen (1,4,7,10-tetraazacyclododecane) bind alkali metal azides? This question is addressed by studying the geometric and electronic structures of the alkali metal azide-cyclen [M(cyclen)N3] complexes using density functional theory (DFT). The effects of adding a second cyclen ring to form the sandwich alkali metal azide-cyclen [M(cyclen)2N3] complexes are also investigated. N3(-) is found to bind to a M(+) (cyclen) template to give both end-on and side-on structures. In the end-on structures, the terminal nitrogen atom of the azide group (N1) bonds to the metal as well as to a hydrogen atom of the cyclen ring through a hydrogen bond in an end-on configuration to the cyclen ring. In the side-on structures, the N3 unit is bonded (in a side-on configuration to the cyclen ring) to the metal through the terminal nitrogen atom of the azide group (N1), and through the other terminal nitrogen atom (N3) of the azide group by a hydrogen bond to a hydrogen atom of the cyclen ring. For all the alkali metals, the N3-side-on structure is lowest in energy. Addition of a second cyclen unit to [M(cyclen)N3] to form the sandwich compounds [M(cyclen)2N3] causes the bond strength between the metal and the N3 unit to decrease. It is hoped that this computational study will be a precursor to the synthesis and experimental study of these new macrocyclic compounds; structural parameters and infrared spectra were computed, which will assist future experimental work.
authors.affiliation: Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit, 80837, Mauritius.
authors.forename: Hanusha
authors.identifier: http://orcid.org/0000-0002-6283-6693
authors.initials: H
authors.lastname: Bhakhoa
authors.affiliation: Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit, 80837, Mauritius.
authors.forename: Lydia
authors.identifier: http://orcid.org/0000-0002-8624-8431
authors.initials: L
authors.lastname: Rhyman
authors.affiliation: School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK.|Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
authors.forename: Edmond P F
authors.identifier: http://orcid.org/0000-0002-1775-0065
authors.initials: EP
authors.lastname: Lee
authors.affiliation: Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit, 80837, Mauritius. ramchemi@intnet.mu.|Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh, 11451, Saudi Arabia. ramchemi@intnet.mu.
authors.forename: Ponnadurai
authors.identifier: http://orcid.org/0000-0002-7272-3561
authors.initials: P
authors.lastname: Ramasami
authors.affiliation: School of Chemistry, University of Southampton, Highfield, Southampton, SO17 1BJ, UK. jmdyke@soton.ac.uk.
authors.forename: John M
authors.identifier: http://orcid.org/0000-0002-9808-303X
authors.initials: JM
authors.lastname: Dyke
mesh_terms: D001386:Azides / Q000737:chemistry*; D000080027:Cyclams; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D047028:Macrocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D011789:Quantum Theory
chemical_list: D001386:Azides; D000080027:Cyclams; D006571:Heterocyclic Compounds; D047028:Macrocyclic Compounds; D009942:Organometallic Compounds; C038072:cyclen
keywords: alkali metals; azides; density functional calculations; host-guest chemistry; sandwich complexes