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Two cis -dioxomolybdenum complexes based on salan ligands with different backbones are reported. The first complex, dioxido{2,2′-[l,2-phenylenebis(iminomethylene)]bis(phenolato)}molybdenum(VI) dimethylformamide disolvate, [Mo(C 20 H 18 N 2 O 2 )O 2 ]·2C 3 H 7 NO ( Ph LMoO 2 , 1b ), features a phenyl backbone, while the second complex, (6,6′-{[(cyclohexane-1,2-diyl)bis(azanediyl)]bis(methylene)}bis(2,4-di- tert -butylphenolato))dioxidomolybdenum(VI) methanol disolvate, [Mo(C 36 H 56 N 2 O 2 )O 2 ]·2CH 3 OH ( Cy LMoO 2 , 2b ), is based on a cyclohexyl backbone. These complexes crystallized as solvated species, 1b ·2DMF and 2b ·2MeOH. The salan ligands Ph LH 2 ( 1a ) and Cy LH 2 ( 2a ) coordinate to the molybdenum center in these complexes 1b and 2b in a κ 2 N ,κ 2 O fashion, forming a distorted octahedral geometry. The Mo—N and Mo—O distances are 2.3475 (16) and 1.9567 (16) Å, respectively, in 1b while the corresponding measurements are Mo—N = 2.3412 (12) Å, and Mo—O = 1.9428 (10) Å for 2b . A key geometrical feature is that the N—Mo—N angle of 72.40 (4)° in Cy LMoO 2 is slightly less than that of the Ph LMoO 2 angle of 75.18 (6)°, which is attributed to the flexibility of the cyclohexane ring between the nitrogen as compared to the rigid phenyl ring in the Ph LMoO 2 .
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This content will become publicly available on October 3, 2026
Mechanistic Insights into Photocatalytic Reduction and Triplet Sensitization of 4-Azido-1-phenylbutan-1-ones to Selectively Form 2-Phenyl-1-pyrrolines
Organic azides are valuable precursors in synthetic chemistry, particularly for nitrogen-based functionalization through photochemical activation. In this study, the photoreactivities of 4-azido-1-phenylbutan-1-one (1a) and 4-azido-(4-methoxy)phenylbutan-1-one (1b) were investigated using visible-light photocatalysts [Ir(dF(CF3)ppy)2(dtbpy)]PF6 and [Ru(bpy)3]Cl2 to elucidate the mechanistic differences between triplet energy transfer and photoreductive electron transfer pathways. Direct irradiation of 1a in methanol favors the formation of a biradical species via intramolecular H atom abstraction to generate its lowest triplet ketone (T1K) with an (n,π*) configuration, which selectively yields 2-phenyl-1-pyrroline derivative 2a. However, 1b reacts through its less reactive T1K, which has a (π,π*) configuration, to form 2-phenyl-1H-pyrrole as the major product. When sensitized by [Ir(dF(CF3)ppy)2(dtbpy)]PF6, selective excitation of the triplet azido moiety (TA) of both 1a and 1b yields the corresponding pyrroline (2a and 2b) via triplet alkylnitrene (31aN and31bN) formation. In contrast, photoactivation of [Ru(bpy)3]Cl2 in the presence of diisopropylethylamine (DIPEA) results in photoreductive electron transfer, forming azido radical anion intermediates, which cyclize to also yield 2a and 2b. Product studies, cyclic voltammetry, laser flash photolysis, and DFT calculations supported these mechanistic assignments. This work demonstrates complementary approaches to control alkyl azide photoreactivity and unlock new strategies for visible-light-induced nitrogen incorporation.
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- Award ID(s):
- 2400277
- PAR ID:
- 10651133
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- The Journal of Organic Chemistry
- ISSN:
- 0022-3263
- Subject(s) / Keyword(s):
- Photocatalysts, energy transfer and electron transfer, triplet alkylnitrenes
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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