Wavelength-Dependent Photofragmentation of a Mixed-Ligand Cyclometalated Platinum(II) Coordination Compound in a Molecular Beam

Abstract

The photofragmentation of (3-Me-4',6'-dfppy)Pt(dpm) (dfppy = difluorophenylpyridinato; dpm = dipivaloylmethyl or 2,2,6,6,-tetramethyl-3,5-heptanedionato- O, O) in a molecular beam is reported. Time-of-flight mass spectra (TOF-MS) and resonance-enhanced multiphoton ionization (REMPI) data are presented and discussed. The dissociation patterns are strongly wavelength-dependent. With 355 nm excitation, the heaviest mass platinum-containing fragments are Pt(+) and diatomic PtC(+). The formation of PtC(+) is the result of an intramolecular rearrangement on the ligand. During irradiation with 410-500 nm light, the fragmentation pattern changes such that the parent ion and platinum-containing fragments of the parent are formed in abundant yield. The (3-Me-4',6'-dfppy) ligand remains intact and coordinated to platinum, but coordinated (dpm) successively breaks apart. A spin-forbidden charge-transfer absorption band centered at around 460 nm plays an important role in the gas-phase photoexcitation of the parent molecule; it is observed in the REMPI spectrum of the parent ion.

Fluorine in Cyclometalated Platinum Compounds

“…Modification of the cyclometalating ligand allows for tuning of the emission color, and for this reason, several compounds with fluoro substituents have been described. As shown in Figure , these compounds can be prepared from the reaction of K 2 PtCl 4 with the corresponding ligand and using ancillary ligands, such as β-diketonates. , In the search of materials for luminescence-based applications, several types of related complexes, including heteroleptic bis-cyclometalated platinum(IV) ( 15a ), ionic compounds with bulky counterions that suppress intermolecular interactions ( 15b ), and complexes functionalized with triarylboron ( 15c ), have been reported, and their syntheses are outlined in Figure . On the other hand, introduction of a cathecol ligand leads to a paramagnetic complex ( 15d ) with the unpaired electron residing mainly on the cathecol ligand …”

“…The emission properties have been studied for several cycloplatinated compounds with either fluorinated cyclometalating − or fluorinated ancillary ligands, − and some examples are shown in Figures – and , respectively. A study based on [N,C,N] cyclometalated platinum complexes with different substituents, including fluorine ( 16a – 16d in Figure ), shows that most of these compounds are highly emissive and stable to sublimation, making them suitable as phosphorescent emitters for OLEDs. , Complexes exhibiting an efficient blue emission are rare compared to those displaying green or red emission.…”

Biotinylated Platinum(II) Ferrocenylterpyridine Complexes for Targeted Photoinduced Cytotoxicity

“…We have chosen platinum as the metal considering the successful use of this metal-based drug, viz., cisplatin, carboplatin, and oxaliplatin, as a novel chemotherapeutic agent. − Although few platinum­(IV) complexes are used in photoactivated chemotherapy, the potential of platinum­(II) complexes in PDT is yet to be realized. − Platinum complexes show excellent photophysical properties with enhanced triplet-state population upon excitation due to spin–orbit coupling, and photoactive platinum complexes could serve as attractive candidates for PDT. In addition, ligand dissociation from ruthenium and platinum complexes in their excited states often results in dual photochemotherapeutic effects, which offer an oxygen-independent mechanistic action suitable for the treatment of hypoxic solid tumors. , We have earlier shown that platinum­(II) ferrocenylterpyridine (Fc-tpy) complexes are significantly photocytotoxic in cancer cells with low dark toxicity . The Fc-tpy moiety upon binding to platinum­(II) behaves as an excellent photoinitiator within the PDT spectral window (600–800 nm) and generates reactive oxygen species (ROS), which causes cellular damage.…”

“…In addition, ligand dissociation from ruthenium and platinum complexes in their excited states often results in dual photochemotherapeutic effects, which offer an oxygen-independent mechanistic action suitable for the treatment of hypoxic solid tumors. 36,37 We have earlier shown that platinum(II) ferrocenylterpyridine (Fc-tpy) complexes are significantly photocytotoxic in cancer cells with low dark toxicity. 33 The Fc-tpy moiety upon binding to platinum(II) behaves as an excellent photoinitiator within the PDT spectral window (600−800 nm) and generates reactive oxygen species (ROS), which causes cellular damage.…”

Photofragmentation of Gas-Phase Lanthanide Cyclopentadienyl Complexes: Experimental and Time-Dependent Excited-State Molecular Dynamics

“…However, the potential still remains for hydrocarbon contamination in the deposited films. In previous work, we − and others − have shown that photoionization time-of-flight mass spectrometry (PI-TOF-MS) is a useful tool for elucidating photofragmentation mechanisms in gas-phase MOCVD precursors, including processes giving rise to fluoride contamination from frequently used fluorinated precursors.…”