An efficient ionization method of electrospray mass spectrometry: the development of an aromatic-cored matrix that wraps labile metal complexes through molecular recognition

Compound 1a, which possesses a triphenylene core and six tetraethyleneoxide side chains, shows efficient ionization of M(II)-containing (M=Pd, Pt) complexes in electrospray ionization mass spectrometry (ESI-MS). The molecular ion peaks [M]+, which are hardly detected under common ESI-MS conditions, are clearly observed as their [M x (1a)n]+ (n=1-4) adducts. UV-visible and NMR studies reveal that the electron-rich triphenylene core of 1a binds to the electron-deficient frameworks of the M(II) complexes in solution, giving rise to charge transfer (CT) complexes. We suggest that 1a stabilizes the complexes and promotes efficient ionization through unique donor-acceptor molecular recognition.