Intermolecular Interactions of CpFePPh₃(CO)CO(CH₂)₅CH₃: From a Crystalline Solid to a Supramolecular “Iron-Truss” Polymer

Abstract

PPh3CpFe(CO)(CO)(CH2)5CH3 (FpC6) spontaneously forms supramolecular polymers in the solid state. The polymers crystallize slowly over a period of one month and can be recovered by melting the crystals at 65 °C. The rheological profile of FpC6 fits the Maxwell model indicating the presence of chain entanglement. Crystal analysis reveals that FpC6 is able to assemble, via cooperative π–π interactions and weak C–H···O hydrogen bonding, into a duplex chain structure with truss arrangement of iron atoms. Powder X-ray diffraction (PXRD) of the polymers shows a double-peak pattern, characteristic for duplex ladder polymers. FTIR/ATR analysis further supports that carbonyl groups are involved in C–H···O hydrogen bonding responsible for the self-assembly. This discovery opens up new design motifs for organometallic supramolecular polymers.

End Group Functionalization of PFpP Macromolecules Via Fp Migration Insertion Reactions

“…In order to clarify this question, we performed IR analysis of FpC6 (PPh 3 CpFe(CO)(CO)(CH 2 ) 5 CH 3 ), which has a coordination structure similar to the junction unit of the prepared PFpP amphiphiles. [ 20 ] FT-IR spectrum of FPC6 crystal is illustrated in Figure 4 b. As shown in Figure 4 b, in addition to the two absorptions corresponding to terminal and acyl CO at 1909 and 1614 cm −1 , a weak absorption at higher wavenumber is also clearly observed.…”

“…It is therefore a question whether all Fp end groups reacted. In order to clarify this question, we performed IR analysis of FpC6 (PPh 3 CpFe(CO)(CO)(CH 2 ) 5 CH 3 ), which has a coordination structure similar to the junction unit of the prepared PFpP amphiphiles . FT‐IR spectrum of FPC6 crystal is illustrated in Figure b.…”

Aromatic Embrace Motifs for Bulk Supramolecular Polymers

“…[7] Severalr epeated experiments produced either crystal structure 1( Figure S15 ai nt he Supporting Information) or 3( Figure S15 bi nt he Supporting Information). 3days) into crystal structure 3.…”

“…At the same time, crystallisation mustb ep revented. [7] To the best of our knowledge,t hese interactions seem to be too weak to hold the chains together. Ac ommon monomer design strategyi st os eparate the associating end groups by as pacero ro ligomer,w hich provides mobility and helps to prevent crystallisation.…”

“…Monomers must possess sufficiently strong directional intermolecular interactions and enough mobility to assemble into chains in the solid state. [7] Crystala nalysisi ndicated that the interaction between FpC 6 monomers involved CÀH···O hydrogen bonds and p-p stacking. [4h] The dilemma is that strong intermoleculari nteractions favour crystallisation and lower the mobility of the monomer.O nt he other hand, althoughw eak intermolecular interactions can improve the mobility of the monomer,t hey cannoth old the chains together,w hich also results in crystallisation.…”