On the intersystem crossing rate in a Platinum(ii) donor–bridge–acceptor triad

The rates of ultrafast intersystem crossing in acceptor–bridge–donor molecules centered on Pt(II) acetylides are investigated. Specifically, a Pt(II) trans-acetylide triad NAP–[triple bond, length as m-dash]–Pt–[triple bond, length as m-dash]–Ph-CH2-PTZ [1], with acceptor 4-ethynyl-N-octyl-1,8-naphthalimide (NAP) and donor phenothiazine (PTZ), is examined in detail. We have previously shown that optical excitation in [1] leads to a manifold of singlet charge-transfer states, S*, which evolve via a triplet charge-transfer manifold into a triplet state 3NAP centered on the acceptor ligand and partly to a charge-separated state 3CSS (NAP−–Pt–PTZ+). A complex cascade of electron transfer processes was observed, but intersystem crossing (ISC) rates were not explicitly resolved due to lack of spin selectivity of most ultrafast spectroscopies. Here we revisit the question of ISC with a combination and complementary analysis of (i) transient absorption, (ii) ultrafast broadband fluorescence upconversion, FLUP, which is only sensitive to emissive states, and (iii) femtosecond stimulated Raman spectroscopy, FSR. Raman resonance conditions allow us to observe S* and 3NAP exclusively by FSR, through vibrations which are pertinent only to these two states. This combination of methods enabled us to extract the intersystem crossing rates that were not previously accessible. Multiple timescales (1.6 ps to ∼20 ps) are associated with the rise of triplet species, which can now be assigned conclusively to multiple ISC pathways from a manifold of hot charge-transfer singlet states. The analysis is consistent with previous transient infrared spectroscopy data. A similar rate of ISC, up to 20 ps, is observed in the trans-acetylide NAP–[triple bond, length as m-dash]–Pt–[triple bond, length as m-dash]–Ph [2] which maintains two acetylide groups across the platinum center but lacks a donor unit, whilst removal of one acetylide group in mono-acetylide NAP–[triple bond, length as m-dash]–Pt–Cl [3] leads to >10-fold deceleration of the intersystem crossing process. Our work provides insight on the intersystem crossing dynamics of the organo-metallic complexes, and identifies a general method based on complementary ultrafast spectroscopies to disentangle complex spin, electronic and vibrational processes following photoexcitation

System‐centered specification of physico–physiological interactions of sensory perception

International audienceThe system‐centered informal representation of a local reality is originally built intentionally by a “sentient being” who is aware that a real situation requires a certain wholeness. The work is based on a pragmatic body of interdisciplinary knowledge constitutive of a system‐centered architecting specification, in harmony with human‐centered and technical‐centered multidisciplinary knowledge. It is necessary to inquire about its outwards materiality as an integrative foundation of multidisciplinary systems engineering, respectively technical and human‐centered. Formalizing the physico‐physiological interaction under investigation combines certain elements of multidisciplinary knowledge of integrative physiology. The chapter describes what enables the tangibility of the togetherness of the sensory perception interaction between an “artifact‐source” of an alarm and a “human‐sink” of control, as a necessary condition. The model of human‐centered intelligent measurement is orchestrated in silico in a first step by the system architect throughout the co‐simulation bus for partial system validation