A Planar Water Tetramer with Tetrahedrally Coordinated Water Embedded in a Hydrogen Bonding Network of [Tc₄(CO)₁₂-(μ₃-OH)₄·4H₂O]

Observation of a water–anion layer constructed from water tetramers and nitrate anions in the crystal host of a cobalt complex

“…The OÁ Á ÁO distances for the hydrogen bonds within the clusters A and B are 2.783 and 2.766 Å , respectively, with an average value of 2.775 Å . They are comparable with that of 2.743 Å calculated for the udud water tetramer [31], but significantly shorter than 2.94 Å found in the discrete water tetramer [10] and 2.896 Å in the water tetramer chain [11], in both cases the tetramer consists of tetracoordinated water molecules. In particular, the OÁ Á ÁO distances in the present tetramers are shorter than that of 2.834 Å measured in the uudd tetramer with tricoordinated water molecules encapsulated in a metal-organic framework [9].…”

“…The crystal host may provide an alternative environment for stabilizing the configuration of water tetramer. The absolute potential energy minimum configuration, the so-called udud form (Chart 1), in which the free hydrogen atoms alternate their positions above (up) and below (down) the ring plane, has been confirmed by vibration-rotation tunneling spectroscopy in gas phase [26] and by X-ray crystallography in an organic crystal host [10]. The less stable uudd tetramer has also been observed in the crystalline solid of a metal complex [9].…”

“…In general, each water monomer in an assembly of water molecules tends to achieve four-coordination, two as acceptors and the other two as donors, as observed in an organic crystal host [11] and in a metal complex [10]. However, hydrogen-bond-deficient water molecules with coordination number of the O atoms less than four have been 2.…”

“…For example, the interactions between water and host can be important for the crystallization of proteins [4] and for the stability of metal-organic complexes [5]. This has prompted extensive studies of various small water clusters in recent years [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], including trimer [7,8], tetramer [9-14], pentamer [15], hexamer [16-20] and octamer [21][22][23][24]. Among the small water clusters, the cyclic water tetramer is of particular interest since it either exists as a basic structural unit or acts as a subunit to form octamers or larger aggregates [25].…”

Supramolecular architecture built of Co(II) and a tripodal ligand containing 1-D water tapes with (H2O)16 cluster units

“…The exploration of structural information of water clusters is key to understanding the behavior of water molecules [3]. Considerable attention has been paid to theoretical and experimental studies of water clusters [4][5][6][7][8] to understand the nature of waterwater interactions in bulk water or ice; a number of self-assembled water clusters including tetramers [9,10], pentamers [11,12], hexamers [13,14], octamers [15,16], decamers [17,18], undecamers [19], dodecamers [20,21], tetradecamers [22], hexadecamers [23], 1-D chain [24][25][26], 1-D tape [27][28][29], 2-D layer [30][31][32][33][34], and 3-D networks [35] have been reported. This work presents structural configurations of water and also provides new insights into the role of water in framework structures.…”