5,11,17,23-Tetra-tert-butyl-25,27-dihydroxy-26,28-bis(tetrazole-5-ylmethoxy)calix[4]arene has been reported to form remarkable Ln19 and Ln12 elongated clusters, upon addition of aqueous ammonium carboxylates. The impact of the <i>para</i> substituent on lanthanoid cluster formation has been studied by synthesising two new bis-tetrazole calixarenes, with <i>p</i>-H, and <i>p</i>-allyl substituents. Solution phase dynamic light scattering measurements of the reaction mixtures indicated that clusters are not formed with the <i>p</i>-H and <i>p</i>-allyl derivatives, in contrast with the behaviour of the <i>t-</i>butyl analogue. Lanthanoid complexes of the <i>p</i>-H and <i>p</i>-allyl calixarenes were characterised by single crystal X-ray diffraction, and were found to form mononuclear complexes, linked to form a one-dimensional coordination polymer for the <i>p</i>-allyl system. All of the complexes were isolated as ammonium salts, with ammonium cation included in the calixarene cavity in most cases. It is concluded that the nature of the <i>para</i> substituent has a profound impact on the lanthanoid cluster formation process, and derivatives with more subtle structural changes will be required to determine if additional lanthanoid “bottlebrush” clusters can be isolated.<br><br>
Influence of the Para-Substituent in Lanthanoid Complexes of Bistetrazole Substituted Calix[4]arenes
