title: Structural identification of a novel axially chiral binaphthyl fluorene based salen ligand in solution using electronic circular dichroism: a theoretical-experimental analysis.
abstract: A novel axially chiral binaphthyl fluorene based salen ligand, AFX-155 [2,2'-(1E,1'E)-(R)-1,1'-binaphthyl-2,2'-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(4-((7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-l)ethynyl)phenol)], with potential applications in homogeneous catalysis, biophotonics, and sensing was synthesized. A full comparative theoretical-experimental analysis of the UV-vis and electronic circular dichroism (ECD) spectra of the 10 primary isomers, comprising stereoisomers and optical isomers, revealed the presence of the unique structure in tetrahydrofuran (THF) solution, the trans-R-intra//trans-R-extra. A proposed route of attack of the (R)-(+)-2,2'-diamino-1,1'-binapthalene onto a salicaldehyde 5-(2-(2-(diphenylamino)-9,9-dihexyl-9H-fluoren-7-yl)ethynyl)-2-hydroxybenzaldehyde followed by a consecutive attack of the resulting species onto another salicaldehyde, both via Burgi:Dunitz trajectory, validates the unambiguous formation of the established isomer. Steric hindrances seem to be the determinant factor that defines the 3D structural conformation of this particular stereoisomer of AFX-155 with triple axial chirality.  The determination of every optimal structure and the dominant conformers of AFX-155 were calculated evaluating, in CONFLEX, their steric energies using force fields at MMFF94S (2006-11-24HGTEMP) level in gas phase. The geometry of the conformers was optimized in THF (using PCM) using Gaussian 09 at the DFT/B3LYP level of theory and 6-31G* basis set. The first 100 electronic excited states were calculated using the same level of theory and basis set.
authors.affiliation: Department of Chemistry, University of Central Florida, P.O. Box 162366, Orlando, Florida 32816-2366, USA.
authors.forename: Carlos
authors.initials: C
authors.lastname: Diaz
authors.forename: Andrew
authors.initials: A
authors.lastname: Frazer
authors.forename: Alma
authors.initials: A
authors.lastname: Morales
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Belfield
authors.forename: Supriyo
authors.initials: S
authors.lastname: Ray
authors.forename: Florencio E
authors.initials: FE
authors.lastname: Hernández
mesh_terms: D002942:Circular Dichroism; D005029:Ethylenediamines / Q000737:chemistry*; D005449:Fluorenes / Q000138:chemical synthesis / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*; D011789:Quantum Theory; D012996:Solutions
chemical_list: D005029:Ethylenediamines; D005449:Fluorenes; D008024:Ligands; D009281:Naphthalenes; D012996:Solutions; C041509:fluorene; C011452:disalicylaldehyde ethylenediamine; C412330:1,1'-binaphthyl