A new route to polycondensed aromatics: photolytic formation of dibenzo[fg,op]naphthacene

Ultrafast Excited-State Dynamics of ortho-Terphenyl and 1,2-Diphenylcyclohexene: The Role of “Ethylenic Twisting” in the Nonadiabatic Photocyclization of Stilbene Analogs

“…28,29 Likewise, OTP is thought to photocyclize into 4a,4b-dihydrotripheneylene (DHT) as the first step in the photochemical synthesis of triphenylene. 12,13 We present ultrafast time-resolved interrogations of UV-induced OTP and DPCH nonadiabatic cyclization in THF solution, demonstrating that S 1 nonadiabatic decay occurs in both cases on picosecond time scales and with the formation of ground-state cyclized products. Importantly, DPCH and OTP differ according to the relative flexibility of the central ring that bridges the terminal phenyl groups, a difference reflected in their relative nonadiabatic decay rates.…”

“…5−9 Much of this work has concentrated on nonadiabatic photocyclization, which is central to molecular photoswitching and photochromic material applications 7,8,10,11 as well as light-assisted synthetic strategies. 12,13 Understanding both how energy flows between electronic states and how structural constraints influence nonadiabatic cyclization pathways is critical for determining how to control bond formation effectively in these applications.…”

“…Nonadiabatic transitions and crossings through conical intersections (CIs) have become paradigmatic concepts for describing the dynamics of electronically excited states and underlie processes ranging from photodissociation of small molecules to the isomerization of large pigments critical to biological processes such as vision. − Capturing glimpses of crossings between electronic states as they occur in time and assessing how they are influenced by molecular structure has become a common goal for experimental research in molecular-energy transfer in recent years. − Much of this work has concentrated on nonadiabatic photocyclization, which is central to molecular photoswitching and photochromic material applications ,,, as well as light-assisted synthetic strategies. , Understanding both how energy flows between electronic states and how structural constraints influence nonadiabatic cyclization pathways is critical for determining how to control bond formation effectively in these applications.…”

“…In this work we have investigated how structural variation gives rise to different nonadiabatic photocyclization behavior for two stilbene analogs, 1,2-diphenylcyclohexene (DPCH) and o -terphenyl (OTP), with the outlook that work with these analogs structurally inhibited against cis–trans isomerization can help to clarify critical features of the CS ring-closure pathway. ,,, DPCH can be viewed as CS structurally constrained against cis–trans isomerization through the addition of a bridging aliphatic chain. ,, Previous work with DPCH has shown that, much like CS, DPCH has a short-lived S 1 state (<20 ps) and cyclizes to form 9,10-cyclohexano-4 a ,4 b -dihydrophenanthrene (CDHP). , Likewise, OTP is thought to photocyclize into 4 a ,4 b -dihydrotripheneylene (DHT) as the first step in the photochemical synthesis of triphenylene. , We present ultrafast time-resolved interrogations of UV-induced OTP and DPCH nonadiabatic cyclization in THF solution, demonstrating that S 1 nonadiabatic decay occurs in both cases on picosecond time scales and with the formation of ground-state cyclized products. Importantly, DPCH and OTP differ according to the relative flexibility of the central ring that bridges the terminal phenyl groups, a difference reflected in their relative nonadiabatic decay rates.…”

Structural Control of Nonadiabatic Bond Formation: The Photochemical Formation and Stability of Substituted 4a,4b-Dihydrotriphenylenes

“…25 Once formed, DHT can subsequently react with a strong oxidant (e.g., I 2 ) to form triphenylene via H abstraction, a process that competes with thermally activated ring reopening. 24 Photochemical studies with OTP were key to determining the optimal reaction conditions for the photoinduced cyclodehydrogenation of ortho-arenes; in fact, under optimal reaction conditions OTP can be converted to triphenylene in very high yield (>90% yield). 24,26 In contrast, lower product yields are generally obtained from similar photochemical reactions with more complex ortho-arene reactants under the same conditions.…”