Preparation and Evaluation of 1,3-alternate 25,27-Bis-[p-nitrobenzyloxy]-26,28-bis-[3-propyloxy]-calix[4]arene-bonded Silica Gel Stationary Phase for LC

Polycyclic aromatic hydrocarbons as test probes to investigate the retention behavior of 1,3-alternate calix[4]arene silica-bonded stationary phases

“…The second block comprises different types of aromatic moieties: naphthoyl ([CalixNph] 25,27‐bis[naphthoyloxy]‐26,28‐bis‐[3‐propyloxy]calix[4]arene), phenyl additionally derivatized in the para position by electron‐withdrawing substituents such as p ‐chlorobenzyl ([CalixBzCl] 25,27‐bis[ p ‐chlorobenzyloxy]‐26,28‐bis‐[3‐propyloxy]calix[4]arene), p ‐nitrobenzyl (CalixBzNO 2 ), and pentafluorobenzyl (CalixBzF 5 ) or aliphatic n ‐hexyl groups ([CalixHex] 25,27‐bis[hexyloxy]‐26,28‐bis‐[3‐propyloxy]calix[4]arene) positioned at the upper rim of the calixarene scaffold. All the investigated 25,27‐disubstituted 26,28‐bis‐[3‐propyloxy]calix[4]arene‐bonded silica gel stationary phases were synthesized in our laboratory . The structures of the stationary phases, the carbon content, and the coverage densities of the investigated packing materials are summarized in Fig.…”

“…All the investigated 25, 27‐disubstituted 26,28‐bis[3‐propyloxy]calix[4]arene‐bonded silica gel stationary phases (Fig. ), blocked in 1,3‐ alternate conformation, were synthesized in our laboratory . The ligands were immobilized on LiChrosorb silica gel, with the exception of the 25,27‐bis(pentafluorobenzyloxy)‐26,28‐bis‐(3‐propyloxy)calix[4]arene (CalixBzF 5 ) and 25,27‐bis[ p ‐nitrobenzyloxy]‐26,28‐bis‐[3‐propyloxy]calix[4]arene (CalixBzNO 2 ) phases, which were bonded to Nucleosil silica gel.…”

Investigation of the chromatographic regulation properties of benzyl groups attached to bridging nitrogen atoms in a calixtriazine‐bonded stationary phase

“…These results were attributed to additional hydrogen‐bonding interaction between the hydrogen‐donor substituents in the analytes and the oxygen atoms of the ether bridge . The relationship between structural elements of substituents, aliphatic chains, and aromatic rings with electron‐releasing or electron‐withdrawing groups attached to the 25‐ and 27‐positions in the upper rim of 1,3‐alternate calix[4]arene) and the retention behavior of the stationary phases were investigated by Sliwka‐Kaszynska and coworkers . The aromatic selectivity of CalixBzCl, CalixBzNO 2 , and CalixBzF 5 columns increased with increasing electron deficiency of the phenyl rings attached to the substituent (Cl < NO 2 < F 5 ) with different electron withdrawing efficiencies.…”

“…This aromatic selectivity is attributed to the predominance of charge‐transfer over π–π interactions . Better resolution factors were obtained for aromatic positional isomers on calix[4]arene phases possessing benzene rings with nitro and methoxy groups located in para positions, compared to the phases containing aliphatic substituents or aromatic rings without substituents .…”