Immobilization of paracetamol and benzocaine pro-drug derivatives as long-range self-organized monolayers on graphite.
We show here by means of scanning tunneling microscopy (STM) at the liquid/solid interface that paracetamol and benzocaine molecules bearing a long aliphatic chain can be immobilized on highly oriented pyrolitic graphite (HOPG) as perfectly ordered two-dimensional domains extending over several hundreds of nanometers. In both cases, high-resolution STM images reveal that compounds 1 and 2 self-assemble into parallel lamellae having a head-to-head arrangement. The paracetamol heads of 1 are in a zigzag position with entangled n-dodecyloxy side chains while benzocaine heads of compound 2 are perfectly aligned as a double row and have their palmitic side chains on either sides of the head alignment. We attribute the very long-range ordering of these two pro-drug derivatives on HOPG to the combined effects of intermolecular H-bonding on one side and Van der Waals interactions between aliphatic side chains and graphite on the other side. The 2D immobilization of pro-drug derivatives via a non-destructive physisorption mechanism could prove to be useful for applications such as drug delivery if it can be realized on a biocompatible substrate.
D000082:Acetaminophen / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry*; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000737:chemistry*; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000737:chemistry*; D001566:Benzocaine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D016503:Drug Delivery Systems; D006108:Graphite / Q000737:chemistry*; D006860:Hydrogen Bonding; D008567:Membranes, Artificial; D016252:Microscopy, Scanning Tunneling; D011355:Prodrugs
D018712:Analgesics, Non-Narcotic; D000779:Anesthetics, Local; D008567:Membranes, Artificial; D011355:Prodrugs; D000082:Acetaminophen; D006108:Graphite; D001566:Benzocaine