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Title: A unique series of chromium( iii ) mono-alkynyl complexes supported by tetraazamacrocycles
Described herein is the synthesis and characterization of macrocyclic Cr III mono-alkynyl complexes. By using the meso -form of the tetraazamacrocycle HMC (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane), trans -[Cr(HMC)(C 2 Ph)Cl]OTf ( 1a ), trans -[Cr(HMC)(C 2 Np)Cl]OTf ( 2a ), trans -[Cr(HMC)(C 2 C 6 H 4 t Bu)Cl]OTf ( 3a ), and trans -[Cr(HMC)(C 2 (3,5-Cl 2 C 6 H 3 ))Cl]OTf ( 4a ) complexes have been realized. These complexes were synthesized in high yield through the reaction of trans -[Cr( meso -HMC)(C 2 Ar) 2 ]OTf ( 1b–4b ) with stoichiometric amounts of methanolic HCl. Single crystal X-ray diffraction showed that the trans -stereochemistry and pseudo-octahedral geometry is retained in the desired mono-alkynyl complexes. The absorption spectra of complexes 1a–4a display d–d bands with distinct vibronic progressions that are slightly red shifted from trans -[Cr(HMC)(C 2 Ar) 2 ] + with approximately halved molar extinction coefficients. Time-delayed measurements of the emission spectra for complexes 1a–4a at 77 K revealed phosphorescence with lifetimes ranging between 343 μs ( 4a ) and 397 μs ( 1a ). The phosphorescence spectra of 1a–4a also exhibit more structuring than the bis-alkynyl complexes due to a strengthened vibronic coupling between the Cr III metal center and alkynyl ligands.  more » « less
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Author(s) / Creator(s):
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Date Published:
Journal Name:
Dalton Transactions
Page Range / eLocation ID:
4936 to 4943
Medium: X
Sponsoring Org:
National Science Foundation
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