The organic diammonium salt N,N′-dibenzyl-N,N,N′,N′-tetramethylethylenediammonium dibromide dihydrate, (dbtmen)Br₂.2H₂O (1), was prepared by the reaction of N,N,N′,N′-tetramethyl-ethylenediamine (tmen) with benzyl bromide.1 crystallizes in the triclinic space group$$P\bar 1$$ with the following unit cell dimensions for C₂₀H₃₄Br₂N₂O₂ (M = 494.31):a = 8.6672(6) Å,b = 11.7046(8) Å,c = 11.7731(8) Å, α = 76.988(8)°, β = 88.978(8)°, γ= 76.198(8)γ,V= 1129.26(13) ų, Z=2. Three components, namely the (dbtmen)²⁺ dication, two bromide anions and two crystal water molecules constitute the structural arrangement of1. H₂O molecules are linked to bromide anions via O-H...Br hydrogen bonding interactions resulting in the formation of a four-membered O₂Br₂ cyclic dibromide. The O₂Br₂ units and the dications are arranged as alternating layers extending in the crystallographicbc plane. The arrangement of anions and cations may be viewed as a typical lamellar structure. The crystal water molecules can be removed by heating 1 at 140°C and the anhydrous dibromide thus formed can be fully rehydrated as evidenced by IR spectra and X-ray powder patterns.

The reaction of benzyl chloride with tetramethylethylenediamine (tmen) results in the formation of the quaternary diammonium dichloride trihydrate (dbtmen)Cl₂.3H₂O 1 (dbtmen is N,N'-dibenzyl-N,N,N',N'-tetramethylethylenediammonium) in good yields. 1 crystallises in the monoclinic $P2_1/c$ space group and its structure consists of N,N'-dibenzyl-N,N,N',N'-tetramethylethylenediammonium dication, two chloride anions and three crystal water molecules all of which are located in general positions. The organic dication is H-bonded to the chloride anions and the crystal waters with the help of intra- and intermolecular C-H$\cdots$Cl and C-H$\cdots$O interactions, while the chloride anions are linked to the crystal waters via O-H$\cdots$Cl interactions. One of the crystal waters is linked through an intermolecular O-H$\cdots$O bond with another water resulting in the formation of a water dimer. The O-H$\cdots$Cl and O-H$\cdots$O interactions between the chloride anions and water molecules lead to the formation of a five-membered {O₃Cl₂} cyclic dichloride containing a water dimer. The five-membered rings are linked into a chain with the aid of a O-H$\cdots$Cl interaction. The organic cations are organised in zigzag fashion on either side of the chain and are further linked to the anionic water chain via weak C-H$\cdot$O and C-H$\cdots$Cl interactions, leading to the supramolecular organisation of the rings into a spiral-like of chain.

The aqueous reaction of [Mg(H₂O)₆]Cl₂ with the in situ generated sodium salt of 4-nitrobenzoic acid (4-nbaH) and N-methylimidazole (N-MeIm) results in the formation of the dinuclear complex [Mg(H₂O)(N-MeIm)₂(4-nba)₂]₂ 1 (4-nba = 4-nitro benzoate), while the direct reaction of [Mg(H₂O)₆]Cl₂ with sodium 4-nba leads to the formation of the mononuclear complex, [Mg(H₂O)₆](4-nba)₂.2H2O 2. In the centrosymmetric dimer 1, each Mg atom is coordinated to an aquo ligand, two monodentate N-MeIm ligands and a monodentate 4-nba ligand. The second 4-nba ligand functions as a bridging bidentate ligand, linking the metal centers and completes the hexacoordination around each Mg(II). The dimeric molecules of 1 are linked into a one-dimensional chain along 𝑏 with the aid of intra- as well as intermolecular H-bonding interactions between the coordinated water and the free oxygen atom of the monodentate 4-nba ligand. In the mononuclear complex [Mg(H₂O)₆](4-nba)₂.2H₂O 2, the Mg(II) is located on an inversion center and its structure consists of an octahedral [Mg(H₂O)₆]²⁺ dication, a free uncoordinated 4-nba anion and a lattice water molecule. One of the H atoms attached of the lattice water is disordered over two positions. The hexaaquomagnesium(II) dication, the 4-nba anion and the lattice water molecule are linked by intra- and intermolecular H-bonding interactions resulting in the formation of alternating layers of [Mg(H₂O)₆]²⁺ dications and 4-nba anions in the crystallographic $bc$ plane. The lattice water molecules are situated between the cations, while the 4-nba anions are arranged antiparallel to each other along 𝑏.

Aqueous reaction of ammonium thiosulfate with piperazine (pip) results in the formation of the title compound (pipH₂)[S₂O₃]$\cdot$H₂O 1 (pipH₂ = piperazinediium) in good yield. 1 was characterized by elemental analysis, IR, Raman andNMRspectra, X-ray powder pattern and its structure was determined. On heating at 100°C, 1 transforms to anhydrous piperazinediium thiosulfate 2, which can be rehydrated to the monohydrate on exposure tomoisture. The structure of 1 consists of two crystallographically independent piperazinediium (pipH₂)²⁺ cations located on inversion centers, a thiosulfate anion and a lattice water. The organic cations, thiosulfate anion and lattice water are linked by six varieties of hydrogen bond namely O-H$\cdots$O, O-H$\cdots$S, N-H$\cdots$O, N-H$\cdots$S, C-H$\cdots$O and C-H$\cdots$S, leading to the formation of alternating layers of (pipH₂)²⁺ cations and water linked thiosulfate chains. A comparative study of several compounds charge balanced by the piperazinediium cation is described.

The synthesis, crystal structure, spectral characterization, photochemistry, electrochemical and thermal studies of the hexakis(butan-1-aminium) heptamolybdate(VI) tetrahydrate (1) are reported. Dissolution of a mixed mono-hepta compound (BuNH₃)₈[(Mo₇O₂₄)(MoO₄)]·3H₂O in water results in its transformation to the title compound viz., (BuNH₃)&#8326 [Mo₇O₂₄]·4H₂O 1 (BuNH₃ = butan-1-aminium). The structure of the title compound consists of two crystallographically unique [Mo₇O₂₄]⁶⁻ anions, twelve independent (BuNH₃)⁺ cations and eight unique lattice water molecules, all of which are interlinked with the aid of three varieties of Hbonding interactions. Solar irradiation of 1 results in the formation of a bis(μ2-oxo) bridged diheptamolybdateproduct. Electrochemical studies reveal the role of 1 in the photodimerization process. Thermal decomposition of 1 results in the formation of crystalline α-MoO₃.