Cr(III)-HMC (HMC = 5,5,7,12,12,14-Hexamethyl-1,4,8,11-tetraazacyclotetradecane) Alkynyl Complexes: Preparation and Emission Properties

Abstract

Presented here is the chemistry of Cr(III) alkynyl complexes based on the rac-HMC and meso-HMC ligands (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane). Thus far, two pairs of cis/trans-[Cr(rac/meso-HMC)(C2R)2]Cl (R = Ph, C2H/C2SiMe3) complexes have been synthesized from reactions between cis/trans-[Cr(rac/meso-HMC)Cl2]Cl and LiC2R. These complexes were characterized using single crystal X-ray diffraction, UV-vis spectroscopy, FT-IR spectroscopy, and fluorimetry. Single crystal X-ray diffraction studies revealed that these complexes adopt a pseudo-octahedral geometry. The electronic spectra of both the cis- and trans-[Cr(rac/meso-HMC)(C4R')2]Cl (R' = H or SiMe3) complexes exhibit d-d bands with pronounced vibronic progression associated with the asymmetric stretch of the Cr-bound C≡C bonds. All of these complexes are phosphorescent and show structured emissions originating from the ligand field excited states.

Synthesis and Investigation of Macrocyclic CrIII Bis(alkynyl) Complexes: Structural and Spectroscopic Properties

“…In complex [ 1 ]Cl, the Cr–C bond length of 2.089(2) Å is comparable to the averaged value of 2.085[2] Å for the Cr–C bonds in trans ‐[Cr(HMC)(C 2 Ph) 2 ]Cl and slightly elongated vs. the averaged bond length for the cyclam analogue, trans ‐[Cr(cyclam)(C 2 Ph) 2 ]OTf (2.073[4] Å) . As expected, the C≡C bond length of 1 + falls into the range of accepted values for a carbon–carbon triple bond at 1.213(3) Å, and is identical to the averaged lengths observed for trans ‐[Cr(HMC)(C 2 Ph) 2 ]Cl (1.211[2] Å), and trans ‐[Cr(cyclam)(C 2 Ph) 2 ]OTf (1.216[5] Å) within experimental errors.…”

“…The emissive nature of Cr III complexes is well established , , , . Because of the pseudo‐octahedral geometry adopted by the complexes [ 1 ]Cl, [ 3 ](BPh 4 ) and [ 4 ]Cl, the transitions can be narrowed to two possible spin‐allowed excitations: the ground state 4 A 2g to either 4 T 1g or 4 T 2g .…”

Crystal structures of 5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane cobalt(III) mono-phenylacetylide and bis-phenylacetylide

“…Alkynyl complexes of 3d metals supported by cyclam (1,4,8,11-tetraazacyclotetradecane) and its C-functionalized derivatives have received intense attention in recent years (Ren, 2016). Interesting examples include magnetic couplings between Cr(cyclam) species mediated by ethynyltetrathiafulvalene ligands (Nishijo et al, 2011), formation of Co III (cyclam) dimers and trimers through 1,4-diethynylbenzene and 1,3,5-triethynylbenzene bridges, respectively (Hoffert et al, 2012), and phosphorescence from [Cr(cyclam')(C 2 R) 2 ] type complexes with cyclam' as either 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (HMC;Tyler et al, 2016) or 5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane (DMC;Judkins et al, 2017). A number of Co III -containing species have been elaborated in our laboratories, including the series [Co(cyclam)Cl] 2 (m-C 2m ) (m = 2 -6; Cook et al, 2015Cook et al, , 2016, the species containing cross-conjugated gem-DEE ligands ISSN 2056-9890 (Natoli et al, 2015(Natoli et al, , 2016, and the unsymmetric trans-[Co(cyclam)(C 2 Ar)(C 2 Ar')] type complexes (Banziger et al, 2015).…”

Synthesis and Characterizations of Macrocyclic Cr(III) and Co(III) 1-Ethynyl Naphthalene and 9-Ethynyl Anthracene Complexes: An Investigation of Structural and Spectroscopic Properties

“…During recent years, our laboratory, along with those of Berben, Shores, Nishijo, − and Wagenknecht, have developed alkynylation chemistry of M III (cyclam) (cyclam = 1,4,8,11-tetraazacyclotetradecane) with M as Cr, Fe, − and Co. − In addition, we also investigated the synthesis and emission properties of Cr III (cyclam′) alkynyl complexes, where cyclam′ is the C- substituted cyclam HMC (5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) or DMC (5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane) . While arylalkynyls with aryl as phenyl or its derivatives have been exploited frequently in these studies, alkynyls with expanded aromatic substituents were limited to the examples of Rh III /Cr III (cyclam) with Ar as naphthalene and phenanthrene .…”