Photophysical Tuning of σ-SiH Copper-Carbazolide Complexes To Give Deep-Blue Emission

Abstract

A series of σ-SiH copper complexes with different carbazole derivatives have been synthesized and characterized that adopt a neutral Si H P 2 ligand (Si H P 2 = (2-i Pr 2 PC 6 H 4 ) 2 Si H Me) and present photophysical properties. A previously reported copper complex (Si H P 2 )Cu(carbazolide), and its derivatives showed that tuning of the emission properties is possible by incorporating various substituents on the carbazolide moiety. Newly synthesized copper complexes (2−6) having 3,6-dichlorocarbazolide, 3,6dibromocarbazolide, 1-fluorocarbazolide, 3,6-dimethylcarbazolide, and 3,6diphenylcarbazolide show a range of λ max values of emission from 418 to 511 nm. Detailed analysis supports that their emission bands originate from excited states with Cu metal−ligand charge transfer (MLCT) and/or ligand-centered (LC) π−π* transitions. Substitution of a methyl or trifluoromethyl group at the 1-position of the carbazolide moiety was also investigated to regulate the structural tuning of the copper emitters. From the X-ray crystallographic data of (Si H P 2 )Cu(1-methylcarbazolide) ( 7) and (Si H P 2 )Cu(1,3-di(trifluoromethyl)carbazolide) (8), unusual structural features, arising from the interaction of a SiH moiety with CH 3 and CF 3 , respectively, were recognized. Such interaction forces the carbazolide moiety to tilt, while the copper geometry remains consistent with the other complexes. In the case of 8, a SiH•••F 3 C interaction locks the carbazolide moiety in place, restricting its orbital overlapping with a copper-based orbital, according to the theoretical analysis by using density functional theory (DFT) computations. Thus, the unusual tilting results in deep-blue emission with a λ max of 430 nm.

Synthesis of Carbene‐Metal‐Amido (CMA) Complexes and Their Use as Precatalysts for the Activator‐Free, Gold‐Catalyzed Addition of Carboxylic Acids to Alkynes

“…The use of the [Au(OH)(IPr)] (IPr= N,N ’‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) and [Au(NHC)(aryl)] synthons have also contributed to the synthetic repertoire [16,17] leading to gold(I)–NHC amido complexes. In case of copper, phosphine bearing amido complexes have been reported through routes employing lithium amides or KHMDS or NaOH as the base [18–23] . Also, NHC‐bearing complexes have been synthesized by addition of amines to a [CuMe(NHC)] complex (Me=methyl) and in 2017 the Cazin group made use of CsOH to procure copper(I)–NHC azolyl complexes which are efficient precatalysts in the hydrosilylation of ketones [21,24,25] .…”

“…In case of copper, phosphine bearing amido complexes have been reported through routes employing lithium amides or KHMDS or NaOH as the base. [18][19][20][21][22][23] Also, NHC-bearing complexes have been synthesized by addition of amines to a [CuMe(NHC)] complex (Me = methyl) and in 2017 the Cazin group made use of CsOH to procure copper(I)-NHC azolyl complexes which are efficient precatalysts in the hydrosilylation of ketones. [21,24,25] Additionally, a linear Cu I complex, [Cu(BIAN-IPr)(Cbz)], bearing a bulky acenaphthoimidazolylidene-based N-heterocyclic carbene has been reported to exhibit interesting emissive properties.…”

Different Reactivities of (5-Ph2P-Ace-6-)2MeSiH toward the Rhodium(I) Chlorides [(C2H4)2RhCl]2 and [(CO)2RhCl]2. Hirshfeld Atom Refinement of a Rh–H···Si Interaction

“…In comparison to the isoelectronic P-donor sites, the silyl anion sites possess a stronger trans effect and create electron-rich metal centers that are amenable to application in catalysis. , In seminal work, Stobart et al used bis­(phosphinoalkyl)­silanes, such as [R 2 P­(CH 2 ) n ] 2 SiMeH ( I , n = 2, 3), as precursors for the preparation of pincer complexes between the related ligand I′ and metals, such as Pt, Ir, and Ru (Scheme ). It was later shown that these ethylene- and propylene-bridged ligands I′ are rather flexible, rendering the metal complexes kinetically labile, which tentatively precluded any applications in catalysis. , Thus, the more rigid bis­( o -phosphinophenyl)­silanes [R 2 P­( o -C 6 H 4 )] 2 SiMeH ( II ) have been frequently used in reactions with metals, such Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, and Au, which in most cases (except Cu, Au) provided stable pincer complexes with the related ligand II′ . − The ethylene-bridged pincer ligands I′ ( n = 2) and II′ are expected to create bonding situations with similar P–M–P bite angles due to the same number of bridging carbon atoms. Many of these pincer complexes were formed via oxidative addition across the Si–H bonds and feature activated M–H bonds and have found diverse applications in catalysis, including for instance the reduction of carbon dioxide or transfer hydrogenation reactions. − …”

“… It was later shown that these ethylene- and propylene-bridged ligands I′ are rather flexible, rendering the metal complexes kinetically labile, which tentatively precluded any applications in catalysis. , Thus, the more rigid bis­( o -phosphinophenyl)­silanes [R 2 P­( o -C 6 H 4 )] 2 SiMeH ( II ) have been frequently used in reactions with metals, such Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, and Au, which in most cases (except Cu, Au) provided stable pincer complexes with the related ligand II′ . − The ethylene-bridged pincer ligands I′ ( n = 2) and II′ are expected to create bonding situations with similar P–M–P bite angles due to the same number of bridging carbon atoms. Many of these pincer complexes were formed via oxidative addition across the Si–H bonds and feature activated M–H bonds and have found diverse applications in catalysis, including for instance the reduction of carbon dioxide or transfer hydrogenation reactions. − For the coinage metals Cu and Au, no oxidative addition was observed. …”

“…7−47 For the coinage metals Cu and Au, no oxidative addition was observed. 23,39,46 In the case of Cu, the H-silanes [R 2 P(o-C 6 H 4 )] 2 SiMeH (II) (R = Ph) gave rise to weak σ interactions of the type Si−H•••Cu. 23 Very recently, we prepared bis(5-diphenylphosphino-acenaphth-6-yl)methylsilane, (6-Ph 2 P-Ace-5-) 2 SiMeH (III), which undergoes complexation with CuCl and AgCl to give (6-Ph 2 P-Ace-5-) 2 SiMeH•MCl possessing weak agostic interactions of the type Si−H•••M with the putatively closed shell d 10 cations M = Cu + , Ag + .…”