| 释义 |
ligand Chem.|ˈlɪgənd|
[f. L. ligand-us, gerundive of ligāre to bind.]
1. Each of the atoms or groups attached to the central (usually the metal) atom of a co-ordination complex.
1952Jrnl. Chem. Soc. 4757 Inferences from spectral absorption to thermochemical stability are therefore very speculative, particularly if different types of ligand, say ions and neutral dipoles, are being compared. 1964J. W. Linnett Electronic Struct. Molecules viii. 138 This implies that..the tendency to form a multiple bond is about the same for the PF3 ligand as for CO. 1964Oceanogr. & Marine Biol. II. 250 The relative accumulation factors for metals in marine organisms are related, in general, to the stability of the metal ions with ligands. 1971Arch. Biochem. & Biophysics CXLVII. 226/1 At each monomer active site the two iron atoms can be bridged by two small, inorganic ligands.
2. Special Comb.: ligand exchange, exchange of ligands between complexes; ligand field, the electrostatic field produced by the ligands in the vicinity of the central atom; so ligand field theory, the branch of chemical theory which deals with the effect of ligands on the energy levels of the central atom or ion; spec. a theory based on an electrostatic model modified by molecular orbital considerations.
1964Jrnl. Amer. Chem. Soc. LXXXVI. 765 (heading) Rates of rapid ligand exchange reactions by nuclear magnetic resonance line broadening studies. 1973Jrnl. Chromatogr. LXXXVII. 513 A rapid ligand-exchange chromatographic method for the separation of α-amino acids from peptides is presented.
1956Nature 18 Feb. 305/2 A proper consideration of the effect of the ligand⁓field explains why the six-coordinate complexes of nickel are equally stable with the cupric complexes. 1960L. Pauling Nature Chem. Bond (ed. 3) v. 174 In some respects the ligand field theory is closely related..to the valence bond theory. 1966Cotton & Wilkinson Adv. Inorg. Chem. (ed. 2) xxvi. 661 This modified CFT [sc. crystal field theory] is often called ligand field theory, LFT. However, LFT is sometimes also used as a general name for the whole gradation of theories from the electrostatic CFT to the MO [sc. molecular orbital] formulation. 1970W. L. Jolly Synthesis & Characterization Inorg. Compounds xxii. 324 If we were able gradually to decrease the ligand field strength to zero, we would find that each term would gradually approach an energy corresponding to one of the states of the free ion. 1971Orchin & Jaffé Symmetry, Orbitals & Spectra vii. 170 Interpretation of the spectra of inorganic complexes is greatly simplified and successfully integrated by the use of ligand field theory.
So ˈligancy = co-ordination number s.v. co-ordination 5; ˈliganded a., bound to a ligand or ligands.
1960L. Pauling Nature Chem. Bond (ed. 3) ii. 63 A sharp distinction is to be made between the number of atoms bonded to a central atom (the ligancy or coordination number of the central atom) and the number of covalent bonds formed by the central atom (its covalence). Ibid. xiii. 538 The changes from the standard sodium chloride and rutile arrangements, with ligancy 6, to cesium chloride and fluorite, respectively, with ligancy 8, are nearly the same. 1965Phillips & Williams Inorg. Chem. I. v. 157 The presence of shared edges and especially of shared faces in a coordinated structure decreases its stability; this effect is large for cations with large valence and small ligancy. 1967Jrnl. Biol. Chem. CCXLII. 3705/2 If the αβ dimer that reacts with ligand is free in solution, the now liganded dimer, α*β*, can associate with another liganded dimer to produce a liganded tetramer, α2*β2*. 1968Inorg. Chem. VII. 1945/2 There are certain bonding situations common in boron chemistry and uncommon elsewhere that lead to unusual nomenclature problems. These include..excess connectivity or ligancy. 1973Jrnl. Molecular Biol. LXXVI. 238 Hybrids formed in a mixture of HbS and CN met-Hb A would, upon deoxygenation, contain one liganded α chain and one liganded β chain.
Add:[1.] a. (Earlier examples.)
1938Bull. Chem. Soc. Japan XIII. 388 In more special cases, selective absorption bands due to ligands themselves may superpose on those proper to the co-ordination combination. [Note] Throughout this article, the word ligand will be used in its original German sense, i.e., an ion or a molecule co-ordinated in a complex radical. 1948Nature 6 Nov. 746/1 It is seen that the stability of complexes increases steadily to reach a maximum at copper whether the ligands be ammonia, ethylene diammine, propylene diammine or salicylaldehyde.
b. Immunol. A molecule or group which binds to another molecule (usu. a macromolecule) with a high degree of specificity.
1968B. Belleau in E. J. Ariëns Physico-Chem. Aspects Drug Action 207 A fundamental study of the interaction mechanisms of ligands (or small molecules) with macromolecules. 1971Proc. Nat. Acad. Sci. LXVIII. 1047/1 Acting on the hypothesis that in vitro, ACh receptor retains its affinity for cholinergic ligands and binds them reversibly and competitively, we searched for such macromolecules in different excitable tissues. 1978Res. in Reproduction May 2/1 Increasing quantities of serum in particular tubes yields dose-related inhibition of binding of the ligand to the antibody or receptor. 1989B. Alberts et al. Molecular Biol. Cell (ed. 2) vi. 325 Mast cells secrete histamine..when triggered by specific ligands that bind to receptors on their surface. |