Piperazine-1,4-diium bis­(hydrogen 2-propyl-1H-imidazole-4,5-dicarbox­ylate) monohydrate

The title compound, C4H12N2 2+·2C8H9N2O4 −·H2O, is a hydrated proton-transfer compound obtained from 2-propyl-1H-imidazole-4,5-dicarb­oxy­lic acid and piperazine. The asymmetric unit contains one half-cation, one anion and half a water mol­ecule. There is a centre of inversion at the centre of the cation ring and the water molecule O atom lies on a twofold rotation axis. In the crystal, inter­molecular N—H⋯O and N—H⋯N hydrogen bonds help to construct a three-dimensional framework. Almost symmetrical, intramolecular O—H⋯O inter­actions are also observed

Di-μ-benzoato-κ3 O,O′:O;κ3 O:O,O′-bis­[(benzoato-κ2 O,O′)(1,10-phenanthroline-κ2 N,N′)lead(II)]

In the centrosymmetric dinuclear title compound, [Pb2(C7H5O2)4(C12H8N2)2], two Pb2+ ions are connected by two tridentate bridging benzoate anions. The Pb2+ ion is seven-coordinated by five O atoms from three benzoate anions and two N atoms from the 1,10-phenanthroline ligands. The benzoate anions adopt two different coordination modes, one bidentate–chelating and one tridentate bridging–chelating. The three-dimensional supra­molecular framework is achieved by inter­molecular π–π stacking inter­actions, with a shortest centroid–centroid distance of 3.617 (4) Å

Poly[[triaqua­(μ3-4-oxidopyridine-2,6-dicarboxyl­ato)thulium(III)] monohydrate]

In the title coordination polymer, {[Tm(C7H2NO5)(H2O)3]·H2O}n, the TmIII atom is eight-coordinated by a tridentate 4-oxidopyridine-2,6-dicarboxyl­ate trianion, two monodentate anions and three water mol­ecules, forming a distorted bicapped trigonal–prismatic TmNO7 coordination geometry. The anions bridge adjacent TmIII ions into double chains. Adjacent chains are further connected into sheets. O—H⋯O hydrogen bonds involving both coordinated and uncoordinated water mol­ecules generate a three-dimensional supra­molecular framework

Di-μ-benzoato-κ3 O,O′:O′;κ3 O:O,O′-bis­[(benzoato-κ2 O,O′)(1,10-phenanthroline-κ2 N,N′)cadmium]

The dinuclear title compound, [Cd2(C7H5O2)4(C12H8N2)2], lies on a crystallographic twofold axis. The CdII ions are connected by two bridging benzoate anions and each ion is seven-coordinated by five O atoms from three benzoate ligands and by two N atoms from 1,10-phenanthroline. The benzoate ligands adopt two different coordination modes, acting as bidentate and bridging tridentate ligands. The discrete neutral mol­ecules further extend their structure into a three-dimensional supra­molecular framework by inter­molecular π–π [inter­planar distances of 3.392 (4) Å] and C—H⋯π stacking inter­actions [H–mean plane = 2.567 (4) and 2.781 (4) Å]

Design of Single-Molecule Multiferroics for Efficient Ultrahigh-Density Nonvolatile Memories

It is known that an isolated single-molecule magnet tends to become super- paramagnetic even at an ultralow temperature of a few Kelvin due to the low spin switching barrier. Herein, single-molecule ferroelectrics/multiferroics is proposed, as the ultimate size limit of memory, such that every molecule can store 1 bit data. The primary strategy is to identify polar molecules that possess bistable states, moderate switching barriers, and polarizations fixed along the vertical direction for high-density perpendicular recording. First- principles computation shows that several selected magnetic metal porphyrin molecules possess buckled structures with switchable vertical polarizations that are robust at ambient conditions. When intercalated within a bilayer of 2D materials such as bilayer MoS2 or CrI3, the magnetization can alter the spin distribution or can be even switched by 180° upon ferroelectric switching, rendering efficient electric writing and magnetic reading. It is found that the upper limit of areal storage density can be enhanced by four orders of magnitude, from the previous super-paramagnetic limit of ≈40 to ≈106 GB in.−2, on the basis of the design of cross-point multiferroic tunneling junction array and multiferroic hard drive

Poly[diaqua­tris­(μ4-1,3-phenyl­ene­diacetato)­dicerium(III)]

In the title coordination polymer, [Ce2(C10H8O4)3(H2O)2]n, each CeIII atom is nine-coordinated by eight O atoms from six different 1,3-phenyl­enediacetate (pda) bivalent anions and one O atom from a coordinated water mol­ecule, forming a distorted tricapped trigonal–prismatic coordination geometry. Eight CeIII ions and twelve pda ligands form a large [Ce8(pda)12] ring, and four CeIII ions and six pda ligands form a small [Ce4(pda)6] ring. The rings are further connected by the coordination inter­actions of pda ligands and CeIII, generating a three-dimensional supra­molecular framework