Making the invisible visible: improved electrospray ion formation of metalloporphyrins/-phthalocyanines by attachment of the formate anion (HCOO⁻)

Abstract

A protocol is developed for the coordination of the formate anion (HCOO(-)) to neutral metalloporphyrins (Pors) and -phthalocyanines (Pcs) containing divalent metals as a means to improve their ion formation in electrospray ionization (ESI). This method is particularly useful when the oxidation of the neutral metallomacrocycle fails. While focusing on Zn(II)Pors and Zn(II)Pcs, we show that formate is also readily attached to Mn(II), Mg(II) and Co(II)Pcs. However, for the Co(II)Pc secondary reactions can be observed. Upon collision-induced dissociation (CID), Zn(II)Por/Pc·formate supramolecular complexes can undergo the loss of CO2 in combination with transfer of a hydride anion (H(-)) to the zinc metal center. Further dissociation leads to electron transfer and hydrogen atom loss, generating a route to the radical anion of the Zn(II)Por/Pc without the need for electrochemical reduction, although the Zn(II)Por/Pc may have a too low electron affinity to allow electron transfer directly from the formate anion. In addition to single Por molecules, multi Por arrays were successfully analyzed by this method. In this case, multiple addition of formate occurs, giving rise to multiply charged species. In these multi Por arrays, complexation of the formate anion occurs by two surrounding Por units (sandwich). Therefore, the maximum attainment of formate anions in these arrays corresponds to the number of such sandwich complexes rather than the number of porphyrin moieties. The same bonding motif leads to dimers of the composition [(Zn(II)Por/Pc)2·HCOO](-). In these, the formate anion can act as a structural probe, allowing the distinction of isomeric ions with the formate bridging two macrocycles or being attached to a dimer of directly connected macrocycles.

Addressing Environmental Challenges of Porphyrin Mixtures Obtained from Statistical Syntheses

“…With the successful application of our method for P1 mixtures, we wanted to explore the scope of our semi‐automated cascade; the impact on the environmental factor, as well as accompanying costs. For this purpose, we enlarged our library (Figure 6), by the synthesis of five more porphyrin mixtures ( P2 – P6 ), which comprise of commonly utilized unsymmetrical porphyrins [2,13–15,19,37–47] . The overall yields are summarized in Table 2, together with an overview on the purification parameters, obtained for all porphyrin mixtures.…”

“…For this purpose, we enlarged our library ( Figure 6), by the synthesis of five more porphyrin mixtures (P2-P6), which comprise of commonly utilized unsymmetrical porphyrins. [2,[13][14][15]19,[37][38][39][40][41][42][43][44][45][46][47] The overall yields are summarized in Table 2, together with an overview on the purification parameters, obtained for all porphyrin mixtures. Spectroscopic data of all isolated porphyrins are listed in the Supporting Information.…”

Influence of electronic and molecular structure on the fragmentation dynamic of even-electron carbocationic triangulenes and helicenes in the gas phase

“…Generally, the ion transfer settings vary due to spectra tuning. We have recently published several illustrative examples of the complementary application of QqToF and ion trap instruments …”

Salt Cluster Attachment to Crown Ether Decorated Phthalocyanines in the Gas Phase

“…Scheme 2, top). 53 It is also possible that the Pcs are only held together by π−π interactions, and both the cluster and the charge carrying anions are weakly attached to the zinc atoms from the outside (cf. Scheme 2, bottom).…”