Synthesis and structural diversity of rare earth anthranilate complexes

Four structural classes have been established for rare earth anthranilates, which have been prepared from the lanthanoid chloride or triflate and anthranilic acid (anthH) followed by pH adjustment to 4. [La(anth)3]n is a polymeric complex with nine coordinate lanthanum and bridging tridentate (O,O,O&prime;) anthranilate ligands, whereas [Nd(anth)3(H2O)3] &middot; 3H2O is monomeric with nine coordinate neodymium and solely chelating (O,O) anthranilate groups. Both chelating (O,O) and bridging bidentate (O,O&prime;) ligands are observed in dimeric [Er2(anth)6(H2O)4] &middot; 2H2O, in which erbium is eight coordinate and the water ligands are in a trans arrangement. A polymer is observed for [Yb(anth)3(H2O)]n with solely bridging bidentate (O,O&prime;) ligands and seven coordination for ytterbium. The NH2 groups of the anthranilate ligands are not coordinated to the metal but is unusually involved in hydrogen-bond networks with water molecules for Ln = Er, Yb.<br /

7 The Two Cultures of Logic

put forward his thesis of the Two Cultures [13]. Snow observed that a gulf had appeared between two academic cultures, with engineers and scientists on one side, and scholars in the humanities on the other. Snow lamented that little communication went on across the gulf, so that most representatives of each of the two academic cultures lacks the most basic understanding, and appreciation, of the other. My thesis, in this written homage to Lotfi Zadeh, is that something akin to Snow’s gulf runs through mathematical logic. For even though logic is a science, there are two types of logicians: on one side of the gulf are those who insist on using True and False (and, possibly, Indeterminate or Undefined) as the only possible truth values; on the other side are those logicians who embrace a wealth of different truth values, with True and False as the extremes of a continuum; to denote the latter area of work, which covers a large variety of approaches including (but not limited to) Fuzzy Logic, we shall loosely use the term multi-valued logic. This article is a plea for diplomacy across the gulf. My vantage point is the study of language and communication, first as a theoretical enterprise, then as an area o