Structural versatility of the quasi-aromatic Möbius type zinc(II)-pseudohalide complexes : experimental and theoretical investigations

In this contribution we report for the first time fabrication, isolation, structural and theoretical characterization of the quasi-aromatic Mobius complexes [Zn(NCS)(2)L-I] (1), [Zn-2(mu(1,1)-N-3)(2)(L-I)(2)][ZnCl3(MeOH)](2)center dot 6MeOH (2) and [Zn(NCS)L-II](2)[Zn(NCS)(4)]center dot MeOH (3), constructed from 1,2-diphenyl-1,2-bis((phenyl(pyridin-2-yl)methylene)hydrazono)ethane (L-I) or benzilbis(acetylpyridin-2-yl)methylidenehydrazone (L-II), respectively, and ZnCl2 mixed with NH4NCS or NaN3. Structures 1-3 are dictated by both the bulkiness of the organic ligand and the nature of the inorganic counter ion. As evidenced from single crystal X-ray diffraction data species 1 has a neutral discrete heteroleptic mononuclear structure, whereas, complexes 2 and 3 exhibit a salt-like structure. Each structure contains a Zn-II atom chelated by one tetradentate twisted ligand L-I creating the unusual Mobius type topology. Theoretical investigations based on the EDDB method allowed us to determine that it constitutes the quasi-aromatic Mobius motif where a metal only induces the pi-delocalization solely within the ligand part: 2.44|e| in 3, 3.14|e| in 2 and 3.44|e| in 1. It is found, that the degree of quasi-aromatic pi-delocalization in the case of zinc species is significantly weaker (by similar to 50%) than the corresponding estimations for cadmium systems - it is associated with the Zn-N bonds being more polar than the related Cd-N connections. The ETS-NOCV showed, that the monomers in 1 are bonded primarily through London dispersion forces, whereas long-range electrostatic stabilization is crucial in 2 and 3. A number of non-covalent interactions are additionally identified in the lattices of 1-3

Modulation of coordination in pincer-type isonicotinohydrazone Schiff base ligands by proton transfer

We present here two different coordination polyhedra of pincer type N2O hydrazone based ligands supplemented with thiocyanate ions. The compounds namely [Hg(SCN)2(HL1)] (1) and [Hg(SCN)2(HL2)] (2) have a common isonicotinohydrazone fragment and have been prepared by using a coordination driven self-assembly of the Hg(SCN)2 with two different ligands including 2-benzoylpyridine-isonicotinoylhydrazone (HL1), and 2-acetylpyridineisonicotinoylhydrazone (HL2). In compound 1 the ligand coordinated to the mercury center in the keto form (=N–NH=C=O) whereas, in compound 2, the proton at the hydrazine group have been shifted to the uncoordinated pyridine ring and the ligand acted as a zwitterion. The structures provide a complementary system for proton transfer within the ligand molecule involving the keto-enol tautomerization of amide group and 4-pyridyl N protonation. As a result, the relative location of orbitals and ligands in the complexes are different as well as the bonding strength and the coordination polyhedra. We have also studied electrostatically enhanced π···π (either conventional or involving the chelate ring) interactions observed in the solid state of both compounds and analyzed them using DFT calculations, Molecular Electrostatic Potential surface and the Bader’s theory of atoms in molecules

Providence

Beginning with the Downtown Master Plan in the late 1950s and continuing through the 1980s, the City of Providence has made various attempts to redevelop its central business district using a number of plans. The basic objective of most of these plans has been to stimulate economic activity in the core by concentrating large sums of public and private investment in the CBD. The underlying rationale has been that successful downtown revitalization would have multiplier effects that would in the long run benefit the entire city. © 1988

Agricultural Policies and Regional Disparities in the Third World: The Case of Iran

This article is concerned with the spatial side effects of the efficiency- oriented sectoral economic policies in Third World countries. Taking the case of Iran as an example, the arti cle demonstrates that during the 1949-1978 period, Iran\u27s efficiency- oriented agricultural policies rein forced the problem of provincial dis parities by favoring the development of a few more-developed provinces to the neglect of the rest of Iran. But since the 1979 revolution, Iran\u27s ag ricultural policies have had a favor able impact on the less-developed provinces as evidenced by a slight decline in the interprovincial dispari ties between 1976 and 1984. The ar ticle concludes that in Third World countries, national spatial develop ment cannot be separated from con siderations of national sectoral policies. © 1988, Sage Publications. All rights reserved

Mitigating traffic congestion in suburbs. An evaluation of land-use strategies

Traditionally, traffic congestion was confined to urban areas, particularly the central business districts. However, in the last 20 years automobile congestion and long commutes have spread to suburban areas as well. This article focuses on land-use strategies to ease traffic congestion in suburban areas. The article first reviews the three broad strategies used in the past to mitigate suburban traffic congestion. Second, it examines four emerging land-use strategies proposed to ease congestion: mixed-use suburban employment centers, pedestrian pockets, planned communities, and traditional neighborhood development. Third, the article evaluates the conceptual underpinning of these strategies and their potential effectiveness in mitigating suburban traffic congestion at five levels of transportation planning: trip generation, trip distribution, trip length, mode choice, and route selection. The article ends with a conclusion regarding application of the land-use strategies in American suburbia and their potential effectiveness in mitigating traffic congestion

Redesigning suburbia for walking and transit: Emerging concepts

Suburban sprawl has caused many problems in the last several decades. Of particular concern is overreliance on the automobile and the lack of alternative forms of transportation such as walking, bicycling, and transit. The advocates of neotraditional town planning have developed the traditional neighborhood development (TND) and pedestrian pocket (PP) concepts for redesigning American suburbia to solve its deficiencies. This paper describes these concepts and then evaluates their potential usefulness to allow walking and transit in suburbia. It is concluded that these concepts offer a unique opportunity to integrate land-use and suburban development policies with transportation policy to stop sprawl and create compact, mixed-use communities. However, of the two concepts reviewed, the pedestrian pocket offers a better potential for developing a new suburban growth pattern on a metropolitan scale that is pedestrian- and transitoriented. Its successful implementation depends on the existence of a supportive metropolitan-scale land-use and transportation plan. © ASCE

Prospects and challenges of the proposed intermodal train station at T.F. Green Airport in Rhode Island

This paper focuses on the proposed intermodal train station at T.F. Green Airport in Rhode Island. Specifically, the paper has three objectives. First, it reviews the current conditions and status of the proposed intermodal train station. Second, drawing from the findings of the current conditions, the paper presents a list of primary benefits and challenges that have faced the development of the station. Third, the paper reviews the actions that have been taken and recommended to remove the barriers that have faced the project. The study concludes that although the proposed intermodal train station is a challenging and complex project, its successful development is within reach and the State of Rhode Island and the City of Warwick stand to benefit from it greatly. Benefits in the areas of economic development, improved environmental quality, and greater transportation alternatives clearly outweigh the possible drawbacks of the project. © (2006) by the Transportation Research Forum All rights reserved

Analysis of factors related to the process of rural-to-urban migration in developing countries in Asia

Typescript (photocopy).Digitized by Kansas Correctional Industrie

New towns and future urbanisation in Iran

This paper focuses on the new-town development strategy in Iran and its role in coping with rapid urbanisation. In the past, the Iranian government has used the new-town strategy primarily for deconcentrating the population of rapidly growing large cities. The paper suggests that, first, for several reasons the new-town strategy has not accomplished its objectives in the past and, second, the strategy contradicts the goal of promoting balanced national development. This requires that the government reconsiders its approach to new-town planning, development and management, and integrates the newtown strategy into the national spatial strategy plan

Prospects and Challenges of the Proposed Intermodal Train Station at T.F. Green Airport in Rhode Island

This paper focuses on the proposed intermodal train station at T.F. Green Airport in Rhode Island. Specifically, the paper has three objectives. First, it reviews the current conditions and status of the proposed intermodal train station. Second, drawing from the findings of the current conditions, the paper presents a list of primary benefits and challenges that have faced the development of the station. Third, the paper reviews the actions that have been taken and recommended to remove the barriers that have faced the project. The study concludes that although the proposed intermodal train station is a challenging and complex project, its successful development is within reach and the State of Rhode Island and the City of Warwick stand to benefit from it greatly. Benefits in the areas of economic development, improved environmental quality, and greater transportation alternatives clearly outweigh the possible drawbacks of the project