Photochemistry of CpMn(CO)₃ and Related Derivatives: Spectroscopic Observation of Singlet and Triplet CpMn(CO)₂

Abstract

We report novel photochemistry derived from (η 5 -C 5 H 5 )Mn(CO) 3 (1a), (η 5 -C 5 H 4 Me)Mn(CO) 3 (1b), (η 5 -C 5 Me 5 )Mn(CO) 3 (1c), and (η 5 -indenyl)Mn(CO) 3 (1d). Photolysis (>261 nm, 1 h) of the parent tricarbonyl (1a−d), matrix isolated in argon at 10 K, yields two species: the expected singlet dicarbonyl 1 (η 5 -L)Mn(CO) 2 ( 1 2a−d) and an additional compound assigned as the triplet dicarbonyl 3 (η 5 -L)Mn(CO) 2 ( 3 2a−d). Density functional theory calculations (B3LYP/LANL2DZ) support the structural assignments for 1 2 and 3 2. Natural bond orbital population analyses of 1 2a and 3 2a explain the source of the large coupling (Δν CO 153 cm −1 ) between the carbonyl stretching vibrations in 3 2a. The triplet isomer ( 3 2) is metastable, even at temperatures as low as 10 K. We determined the rate constants for the thermal isomerization 3 2 → 1 2 using dispersive kinetic analysis. As revealed by these rate constants, the triplet complexes display the following order of stability in this system: Ind ≫ Cp ≈ Cp′ > Cp*. The spectroscopy and kinetics observed in various matrices (Ar, CH 4 , and Xe) do not differ appreciably. Experimental and computational results suggest that the singlet−triplet energy gap (ΔE ST ) of CpMn(CO) 2 (2a) must be smaller than previous estimates.

Half sandwich based rhodamine ‐ hydrazone single molecule probe: Light responsive, metal sensing and imaging properties

“…Literature reveals that the cymantrene based half sandwich has the ability to photolytically dissociate a metal carbonyl group creating an electron deficient manganese metal center, which can further be used for derivatization. Additionally, the significant contribution of Mn (I) tricarbonyl type complex for their photo‐triggered CO‐releasing molecular (CORM) behavior[6g] prompted us to investigate the photo‐dissociation mechanism of compound 1 . We, therefore, focused our study to understand the photolytic behavior of compound 1 to introduce the phenomena for light sensing applications.…”

“…Organometallic fragments like, half sandwich cymantrenyl group are significant moieties because of their three legged piano stool type structure involving carbonyl groups attached to manganese atom and for their unique photolytic decarbonylation property. The photo‐dissociation behavior led to a large number of functional derivatives and showed interesting photophysical phenomena . Recently, a Mn (I) tricarbonyl complex has been investigated as a biocompatible CO releasing molecule (CORM), in which the photolytic behavior is used for the release of CO into the cellular matrices [6g].…”

“…The photo‐dissociation behavior led to a large number of functional derivatives and showed interesting photophysical phenomena . Recently, a Mn (I) tricarbonyl complex has been investigated as a biocompatible CO releasing molecule (CORM), in which the photolytic behavior is used for the release of CO into the cellular matrices [6g]. As a part of our ongoing interest in using sandwich and half‐sandwich organometallic fragments for sensor based application and photo‐induced behavior, we focused our study on rhodamine based half sandwich organometallic moieties and exploit their fluorescence and sensing behavior.…”

Spin‐forbidden reactions: computational insight into mechanisms and kinetics

“…The example of Fe(CO) 4 just discussed above is one case which is particularly well understood. The chemistry of the 16‐electron fragments CpMn(CO) 2 and CpCo(CO), derived from photolysis of the corresponding tri‐ and di‐carbonyl complexes, are two more systems that have received extensive attention …”

“…The chemistry of the 16-electron fragments CpMn(CO) 2 and CpCo(CO), derived from photolysis of the corresponding tri-and di-carbonyl complexes, are two more systems that have received extensive attention. [58][59][60]…”