Terpiridina eta terfosfinina pincer deribatuekin funtzionalizatutako polimero metalosupramolekularren autokonpontze gaitasunaren azterketa konputazionala

Abstract

Polimero autokonpongarriek, modu autonomoan konpontzeko erakutsi duten gaitasunagatik interes handia sortu dute materialen zientziaren arloan. Azken hamarkadan, propietate autokonpongarriak aurkeztu dituzten metal-pincer motako koordinazio loturekin funtzionalizatutako hainbat polimero metalosupramolekular garatu izan dira. Hala ere, literaturan ez daude mota honetako polimero autokonpongarrien adibide gehiegi eta propietate autokonpongarriak ematen dizkieten koordinazio loturei buruzko informazioa urria da, autokonpontze mekanismoa osotasunean ulertzen ez delarik. Lan honetan, metal-pincer motako polimero autokonpongarrietan ematen diren elkarrekintza supramolekularrak ulertzeko hainbat koordinazio konplexuren inguruko kalkulu teorikoak egin dira. Koordinazio konplexu hauek osatzen dituzten katioi eta pincer-en polarizagarritasun erlatiboak konplexuaren ezaugarri dinamikoekin erabat erlazionaturik daudela ondorioztatu da. Izan ere, kontrako polarizagarritasuneko katioi eta ligandoez osatuko konplexuek koordinazio lotura dinamikoak sortuko dituztela ikusi da. Pincer-en para posizioetan talde elektroerakarle zein elektroemaileen presentziarekin konplexuen elkarrekintza energia kontrolatu daitekeela egiaztatu da, nahiz eta honek loturaren dinamikotasunean eragina izan dezakeen ez den frogatu. Gainera, konplexuen egitura geometrikoak berauen propietate dinamikoetan eragina izan dezakeela proposatu da, metalaren inguruko gehiegizko dentsitate elektronikoaren eraginezko konplexuen simetrikotasun galeraren erantzule nagusiak ondorioztatu direlarik. Modu honetan, metal-pincer motako koordinazio konplexuen ezaugarri dinamikoetan eragiten duten parametro nagusiak aurkeztu dira, polimero autokonpongarriak egiteko etorkizuneko diseinu parametro bezala erabili daitezkeenak. Irizpide horietan oinarrituz, aztertutako sistemen artean giro tenperaturan propietate autokonpongarriak izateko sistema probableenak proposatu dira.

The ability of self-healing polymers of autonomously repairing themselves has raised great interest in the field of material science lately. Over the last decade, some self-healing metallosupramolecular polymers functionalised with metal-pincer type coordination bonds havebeen reported in the literature. However, examples of this kind of polymers are scarce and information about the coordination bonds responsible for the self-healing properties is limited. In addition, the self-healing mechanism is not entirely understood. In this work, several coordination complexes have been studied by means of theoretical calculations in order to get a better understanding of the metalpincer interaction present in the crosslinked supramolecular networks of this kind of self-healing polymers. The obtained results indicate that the relative polarizabilities of the components of the coordination complexes play a major role in the determination of the dynamic properties of these bonds. In fact, it has been observed that complexes formed by cations and pincers with opposite polarizabilities tend to produce more dynamic coordination bonds. Designing pincers with electron withdrawing or electron donating groups in their para positions has proved to be an appropriate method for tuning the interaction energy of these coordination bonds over a wide range of values. Yet it has not been checked whether that can affect the dynamism of the bond. Moreover, it has been proposed that geometrical structure of the coordination complexes might influence their dynamic properties. The effects responsible for loss of symmetry in the complexes due to the excessive electronic density around the metal centre have also been deduced. Thereby, the main parameters that affect to the dynamic features of metal-pincer type coordination bonds have been outlined so that they can be used as future design parameters for self-healing metal-pincer type metallosupramolecular polymers. By consideration of these criteria, three systems have been chosen among the ones studied as the most probable to exhibit self-healing properties at room temperature.